Deep groove etching method

Abstract

The invention discloses a deep groove etching method. The method comprises the following steps: providing a substrate; a preset groove is formed in the substrate; forming a preset filling layer in the preset groove; performing planarization processing on the preset filling layer to enable the preset filling layer to be flush with the substrate, and forming an epitaxial layer on the substrate; and etching to remove the preset filling layer, and continuously etching on the epitaxial layer along the preset groove to form the target deep groove. The etching process difficulty of the target deep groove is reduced, the side wall of the formed target deep groove is steep, the bottom of the formed target deep groove is flat, and it can be guaranteed that the deep groove reaches the required depth-to-width ratio.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more particularly to a deep trench etching method. Background Technology

[0002] In related technologies, deep trench isolation etching refers to etching trenches tens of micrometers deep using chemical etching processes, followed by polysilicon deposition and chemical mechanical polishing to achieve planarization. Existing technologies form deep trench structures through a single etching process. Limited by the etching depth, these trenches tend to be wide at the top and narrow at the bottom, which is not an ideal shape. A sharp bottom can cause electron accumulation, affecting isolation performance and reliability. Conversely, the top of the trench, due to the long etching time and large contact area with the etching chemicals, can easily become too wide, failing to achieve the required aspect ratio, thus impacting isolation performance and increasing the design area. Therefore, existing deep trench etching technologies struggle to achieve steep, regular sidewall morphologies and flat bottom morphologies. Summary of the Invention

[0003] The technical problem solved by this invention is to provide a deep trench etching method that reduces the difficulty of etching the target deep trench, and the resulting target deep trench has steep sidewalls and a flat bottom, which can ensure that the deep trench achieves the required depth-to-width ratio and improves the isolation effect of the deep trench structure.

[0004] To solve the above-mentioned technical problems, the technical solution of this application is as follows:

[0005] This application provides a method for etching deep trenches, the method comprising:

[0006] Provide substrate;

[0007] Pre-defined trenches are formed on the substrate;

[0008] A preset filling layer is formed in the preset trench;

[0009] The preset filling layer is planarized to make it flush with the substrate, and an epitaxial layer is formed on the substrate;

[0010] The preset filler layer is removed by etching, and the target deep trench is formed by continuing etching along the preset trench on the epitaxial layer.

[0011] Optionally, when the depth of the target trench is greater than the target depth, the step of continuing to etch along the preset trench on the epitaxial layer to form the target trench includes:

[0012] A dry etching process is used to continue etching along the preset trench on the epitaxial layer to form an initial trench; the size of the initial trench is smaller than the size of the target deep trench.

[0013] The initial trench is used as the current trench, and a current filling layer is formed in the current trench; the material of the current filling layer is polycrystalline silicon or oxide;

[0014] The current epitaxial layer is formed in the unfilled region of the substrate;

[0015] The target deep trench is formed by continuing etching along the current trench on the current epitaxial layer.

[0016] Optionally, the step of continuing to etch along the current trench on the current epitaxial layer to form the target deep trench includes:

[0017] Continue etching along the current trench on the current epitaxial layer to form an intermediate trench;

[0018] When the size of the intermediate trench is smaller than the size of the target deep trench, the intermediate trench is used as the current trench again;

[0019] Repeat the steps of forming the current fill layer in the current trench to continue etching along the current trench on the current epitaxial layer to form an intermediate trench, until the size of the intermediate trench is the same as the size of the target deep trench.

[0020] Optionally, forming an epitaxial layer on the target region of the substrate includes:

[0021] The substrate containing the preset filling layer is placed in a cavity at 500-800°C, and a single-crystal silicon epitaxial layer is formed on the target area of ​​the substrate by reacting the epitaxial generation gas with hydrogen; the target area is the area on the substrate other than the preset filling layer.

[0022] Optionally, the difference between the thickness of the epitaxial layer and the preset depth is... The preset depth is the depth difference between the target deep trench and the preset groove; the epitaxial generated gas includes at least one of silicon tetrachloride and tetrachlorohydrocarbon.

[0023] Optionally, the depth of the preset trench is less than the depth of the target deep trench, and the width of the preset trench is less than the width of the target deep trench; the bottom of the target deep trench is flat and the sidewalls are steep.

[0024] Optionally, the depth ratio of the preset groove to the target deep groove is (2-3):6, and the width ratio of the preset groove to the target deep groove is (0.5-0.8):1.

[0025] Optionally, the depth of the target deep groove is 30 micrometers, and the depth of the preset groove is 10-15 micrometers; the width of the target deep groove is 2.0 micrometers, and the width of the preset groove is 1.0-1.6 micrometers.

[0026] Optionally, forming a preset filling layer in the preset trench includes:

[0027] The preset trench is filled with polycrystalline silicon or oxide;

[0028] The filling surface of the preset trench is planarized to form the preset filling layer; the surface of the preset filling layer is flush with the surface of the substrate.

[0029] Optionally, the method further includes:

[0030] The polycrystalline silicon or oxide is filled into the target deep trench;

[0031] The filling surface of the target deep trench is planarized to form a target filling layer; the surface of the target filling layer is flush with the surface of the epitaxial layer.

[0032] Optionally, forming a predetermined trench on the substrate includes:

[0033] Photoresist is coated on the surface of the substrate;

[0034] Obtain the target photomask corresponding to the target deep groove;

[0035] The photoresist is exposed using the target photomask, and the preset trenches are formed on the substrate by adjusting the photolithography conditions;

[0036] The step of continuing to etch along the preset trench on the epitaxial layer to form the target deep trench includes:

[0037] The target deep groove is formed by continuing to etch along the preset trench on the epitaxial layer using the target photomask.

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0039] In the etching process of the target deep trench, the present invention first forms a small preset trench on the substrate, forms a preset filling layer in the preset trench, and then forms an epitaxial layer on the non-filled area of ​​the substrate. The epitaxial layer distinguishes the deep trench location from other locations. After etching away the preset filling layer, the preset trench is further etched on the epitaxial layer to form the target deep trench. This reduces the difficulty of the etching process of the target deep trench, and the formed target deep trench has steep sidewalls and a flat bottom, which can ensure that the deep trench achieves the required aspect ratio and improves the isolation effect of the deep trench structure. Attached Figure Description

[0040] To more clearly illustrate the technical solution of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of a deep trench structure formed by a single etching process using existing technology;

[0042] Figure 2 This is a flowchart of a deep trench etching method provided in an embodiment of the present invention;

[0043] Figures 3 to 8 This is a cross-sectional structural schematic diagram of the formation process of a photoelectric sensor provided in an embodiment of the present invention;

[0044] Figure 9 This is a flowchart of an etching method for a target deep trench provided in an embodiment of the present invention;

[0045] In the figure, the corresponding reference numerals are: 01-substrate, 02-deep trench structure, 03-preset trench, 04-preset filling layer, 05-epitaxy layer, 06-target deep trench, 07-target filling layer. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] As used herein, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of this application. In the description of this application, it should be understood that spatial relative terms, such as "below," "under," "lower part," "above," "upper part," "front," "back," "above," and the like, are used herein for ease of description to describe the relationship between one element or feature as illustrated in the figures and another element(s). These are used only for the convenience of describing this application and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting this application. Spatial relative terms are intended to cover different orientations in the use or operation of the device other than those depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein can be interpreted similarly.

[0048] The following disclosure provides numerous different embodiments or instances for implementing various features of the provided subject matter. Specific examples of elements and configurations are described below to simplify this disclosure. Of course, these elements and configurations are merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the following description may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features may be formed between the first and second features such that the first and second features are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in various instances of this disclosure. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0049] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.

[0050] In related technologies, deep trench isolation etching refers to etching trenches tens of micrometers deep using chemical etching processes, followed by polysilicon deposition and then chemical mechanical polishing to achieve planarization. For example... Figure 1 , Figure 1 This is a schematic diagram of a deep trench structure 02 formed by a one-time etching process using existing technology; the deep trench structure 02 is formed on the substrate 01, and the deep trench structure 02 is a structure that is wide at the top and narrow at the bottom; Figure 1 The process includes two deep trench structures 02, each 30 micrometers deep and 2 micrometers wide at the top. Due to the deep etching depth, the etching chemical gas or liquid may not be able to create a flat morphology when etching to the bottom of the trench, resulting in a sharp or uneven structure. A sharp bottom in the trench may cause electron accumulation, affecting the isolation effect and reliability. Conversely, the top of the trench, due to the long etching time and large contact area with the etching chemical material, may become too wide, failing to achieve the required aspect ratio, thus affecting the isolation effect and increasing the design area. Therefore, existing deep trench etching techniques struggle to achieve steep, regular sidewall morphologies and flat bottom morphologies.

[0051] To address the technical problem in existing technologies where deep trench structures are wide at the top and narrow at the bottom, failing to achieve the required aspect ratio and thus affecting the isolation effect, this application provides a deep trench etching method to solve the aforementioned problems in the prior art.

[0052] Figure 2 This is an exemplary embodiment illustrating a deep trench etching method, such as... Figure 3-8 As shown, Figures 3 to 8 This is a cross-sectional structural diagram of a deep trench formation process provided in an embodiment of the present invention; the method includes:

[0053] S201: Provides substrate 01;

[0054] In embodiments described in this specification, substrate 01 may include a semiconductor die substrate, a semiconductor wafer, or another type of substrate formed from semiconductor pixels. In some implementations, substrate 01 may be formed from silicon, materials including silicon, III-V compound semiconductor materials such as gallium arsenide (GaAs), silicon-on-insulator (SOI), or another type of semiconductor material capable of generating charge from photons of incident light.

[0055] S202: A preset trench 03 is formed on the substrate 01;

[0056] In the embodiments described in this specification, such as Figure 3 As shown, a preset trench 03 is formed on the substrate 01; the size of the preset trench 03 is smaller than the size of the target deep trench 06; the size of the preset trench 03 can be determined according to the size of the target deep trench 06 to be etched, wherein the size of the preset trench 03 is smaller than the size of the target deep trench 06. The preset trench 03 can be rectangular or similar to a rectangle. Figure 2 The preset groove 03 is rectangular.

[0057] S203: A preset filling layer 04 is formed in the preset trench 03;

[0058] In the embodiments described in this specification, the material of the preset filling layer 04 is polycrystalline silicon or oxide; such as Figure 4 As shown, after forming the preset trench 03, polysilicon or oxide material can be filled into the preset trench 03 to form a preset filling layer 04. By forming the preset filling layer 04, the formation position of the epitaxial layer 05 on the substrate 01 can be controlled, avoiding the formation of the epitaxial layer 05 in the corresponding area of ​​the preset trench 03, thereby avoiding repeated etching of the corresponding area of ​​the preset trench 03 and reducing the workload in the subsequent etching process of the target deep trench 06.

[0059] S204: The preset filling layer 04 is planarized so that the preset filling layer 04 is flush with the substrate 01, and an epitaxial layer 05 is formed on the substrate 01.

[0060] The formation of an epitaxial layer on the substrate may include: forming an epitaxial layer 05 on a target region of the substrate 01; the target region is the region on the substrate 01 other than the preset filling layer 04.

[0061] In the embodiments of this specification, an epitaxial layer 05 can be formed on substrate 01 using a selective epitaxy process. Selective epitaxy is a method of growing an epitaxial layer 05 only on monocrystalline silicon and not on other materials. Since substrate 01 is monocrystalline silicon and the preset filler layer 04 is polycrystalline silicon or oxide, the growth of epitaxial layer 05 on the preset filler layer 04 can be avoided. Figure 5 As shown, an epitaxial layer 05 is formed on the target area, i.e., the non-filled area, of the substrate 01; the target area is the area on the substrate 01 excluding the preset fill layer 04. The epitaxial layer 05 can distinguish the location of the target trench 06 from other locations, thereby facilitating subsequent etching of the target trench 06. The formation of the epitaxial layer 05 further deepens the trench, thereby reducing the etching workload during the formation of the target trench 06. The target trench 06 is typically a trench with a depth greater than or equal to 30 micrometers, and the aspect ratio of the target trench 06 can be (10-15):1; for example, the aspect ratio can be 15:1.

[0062] In the embodiments described in this specification, the depth difference between the target deep trench 06 and the preset trench 03 is a preset depth, and the difference between the thickness of the epitaxial layer 05 and the preset depth is a When the depth ratio of the preset trench 03 to the target deep trench 06 is (2-3):6, the ratio of the thickness of the epitaxial layer 05 to the depth of the preset trench 03 is (3-4):6; and additional epitaxy is possible. This is to cover the losses during the process window and subsequent planarization.

[0063] S205: Etch away the preset filling layer 04, and continue etching along the preset trench 03 on the epitaxial layer 05 to form the target deep trench 06.

[0064] In the embodiments described in this specification, such as Figure 6 As shown, after forming the epitaxial layer 05, the preset filling layer 04 can be removed by selective etching. Due to the presence of the epitaxial layer 05, the depth of the remaining empty trench is greater than the depth of the preset trench 03, thereby reducing the etching difficulty of the target deep trench 06; as Figure 7 As shown, etching can continue along the preset trench 03 on the epitaxial layer 05, and the substrate 01 is further etched. At this time, the etching can modify the surface morphology of the deep trench, deepen and widen it to achieve the depth and width required by the high voltage device, thereby forming the target deep trench 06.

[0065] After the epitaxial layer 05 is formed, the trench 03 will naturally form without etching. This is because selective epitaxy is used during epitaxial growth. Selective epitaxy grows only on a substrate (e.g., single-crystal silicon) and not on other materials. During epitaxial growth, the trench 03 is filled with oxide, and single-crystal silicon will not grow on top of the oxide, thus naturally forming voids. The width of these voids matches the size of the trench but is smaller than the width of the target deep trench 06, leaving a process window for the target deep trench.

[0066] In the embodiments of this specification, during the etching process of the target deep trench 06, a small preset trench 03 is first formed on the substrate 01, and a preset filling layer 04 is formed in the preset trench 03. Then, an epitaxial layer 05 is formed on the non-filled area of ​​the substrate 01, and the deep trench location is distinguished from other locations by the epitaxial layer 05. After etching away the preset filling layer 04, the preset trench 03 is further etched on the epitaxial layer 05 to form the target deep trench 06. This reduces the etching process difficulty of the target deep trench 06, and the formed target deep trench 06 has steep sidewalls and a flat bottom, which can ensure that the deep trench achieves the required aspect ratio and improves the isolation effect of the deep trench structure.

[0067] In the embodiments of this specification, the depth of the preset trench 03 is less than the depth of the target deep trench 06, and the width of the preset trench 03 is less than the width of the target deep trench 06; the bottom of the target deep trench 06 is flat and the sidewalls are steep; thereby, electron accumulation caused by forming a deep trench with a sharp bottom can be avoided. The target deep trench 06 in this embodiment improves the isolation effect and reliability.

[0068] In some embodiments, the depth ratio of the preset groove 03 to the target deep groove 06 is (2-3):6, and the width ratio of the preset groove 03 to the target deep groove 06 is (0.5-0.8):1.

[0069] In the embodiments of this specification, the size of the preset trench 03 can be determined according to the size of the target deep trench 06. If two etching operations are performed, the depth ratio of the preset trench 03 to the target deep trench 06 can be set to (2-3):6, and the width ratio of the preset trench 03 to the target deep trench 06 can be (0.5-0.8):1. For example, when the target deep trench 06 is a trench with a depth of 30 micrometers and a width of 2 micrometers, the preset trench 03 can be a trench with a depth of 10-15 micrometers and a width of 1 micrometer.

[0070] In some embodiments, forming a preset filling layer 04 in the preset trench 03 includes:

[0071] The polycrystalline silicon or oxide is filled into the preset trench 03;

[0072] The filling surface of the preset trench 03 is planarized to form the preset filling layer 04; the surface of the preset filling layer 04 is flush with the surface of the substrate 01.

[0073] In the embodiments of this specification, a chemical deposition process can be used to fill the pre-set trench 03 with polysilicon or oxide; then a chemical mechanical polishing process can be used to planarize the filled surface of the pre-set trench 03 until the surface of the pre-set filling layer 04 is flush with the surface of the substrate 01, thereby forming the pre-set filling layer 04, thereby ensuring that the pre-set filling layer 04 is flush with the surface of the substrate 01 and has a flat surface, which facilitates the formation of an epitaxial layer 05 in the non-filled area on the substrate 01.

[0074] In some embodiments, the depth of the target deep groove 06 is 30 micrometers, and the depth of the preset groove 03 is 10-15 micrometers; the width of the target deep groove 06 is 2.0 micrometers, and the width of the preset groove 03 is 1.0-1.6 micrometers.

[0075] In the embodiments of this specification, when the depth of the target deep trench 06 is 30 micrometers and the width is 2.0 micrometers, the depth of the preset trench 03 can be set to 10-15 micrometers and the width to 1.0-1.6 micrometers; thereby facilitating the formation of the target deep trench 06 through two or more etching processes.

[0076] In some embodiments, forming the epitaxial layer 05 on the target region of the substrate 01 includes:

[0077] The substrate 01 containing the preset filling layer 04 is placed in a cavity at 500-800°C, and a single-crystal silicon epitaxial layer 05 is formed on the target area of ​​the substrate 01 by reacting the epitaxial generated gas with hydrogen.

[0078] In the embodiments of this specification, the epitaxial generated gas includes at least one of silicon tetrachloride and tetrachlorohydrocarbon.

[0079] In the embodiments of this specification, the temperature of the selective epitaxial process can be controlled at 500-800°C, and the epitaxial generation gas can be silicon tetrachloride, tetrachlorohydrocarbon, or other silicides, thereby forming a single-crystal silicon epitaxial layer 05.

[0080] In some embodiments, when the depth of the target trench is greater than the target depth, the step of continuing to etch along the preset trench 03 on the epitaxial layer 05 to form the target trench 06 includes:

[0081] A dry etching process is used to continue etching along the preset trench 03 on the epitaxial layer 05 to form an initial trench; the size of the initial trench is smaller than the size of the target deep trench 06.

[0082] The initial trench is used as the current trench, and a current filling layer is formed in the current trench; the material of the current filling layer is polycrystalline silicon or oxide;

[0083] The current epitaxial layer is formed in the unfilled region of the substrate 01;

[0084] The target deep trench 06 is formed by continuing etching along the current trench on the current epitaxial layer.

[0085] In the embodiments of this specification, when the depth of the target trench is greater than the target depth, and two etching operations are insufficient to reach the target trench depth, multiple epitaxial operations can be performed to approximate the target trench depth. The thickness of each epitaxial operation can be adjusted according to the actual process capability. For example, the preset depth of the first etching on the substrate does not exceed 15 micrometers. More than three etching operations are required to form the target trench, where the target depth can be set according to the actual situation; for example, the target depth can be set to 30 micrometers. The gas used in the dry etching process can be one or more of HBr, Cl2, and HCl. For example, three etching operations can be performed: first, etching to form the trench; second, etching away the oxide in the preset trench after the epitaxial layer has grown; third, etching the target trench.

[0086] After the first etching forms the preset trench 03, a second etching can be performed to form an initial trench that is larger than the preset trench 03 but smaller than the target deep trench 06. A filling layer and an epitaxial layer 05 are formed in the initial trench, and the target deep trench 06 can be further etched on the epitaxial layer 05. At this time, the target deep trench 06 can be formed by etching the trench at least three times.

[0087] In this embodiment of the specification, the step of continuing to etch along the current trench on the current epitaxial layer to form the target deep trench 06 includes:

[0088] Continue etching along the current trench on the current epitaxial layer to form an intermediate trench;

[0089] When the size of the intermediate trench is smaller than the size of the target deep trench 06, the intermediate trench is re-designated as the current trench.

[0090] Repeat the steps of forming the current fill layer in the current trench to continue etching along the current trench on the current epitaxial layer to form an intermediate trench, until the size of the intermediate trench is the same as the size of the target deep trench 06.

[0091] In the embodiments of this specification, the target deep trench 06 can also be formed by etching trenches multiple times; an intermediate trench can be formed by continuing to etch along the current trench on the current epitaxial layer; when the size of the intermediate trench is smaller than the size of the target deep trench 06, the intermediate trench is used as the current trench again; the steps of forming the current filling layer in the current trench to continuing to etch along the current trench on the current epitaxial layer to form the intermediate trench are repeated until the size of the intermediate trench is the same as the size of the target deep trench 06.

[0092] For example, the target deep trench 06 can be formed by four etching processes, the method comprising:

[0093] Substrate 01 is provided;

[0094] A preset trench 03 is formed on the substrate 01 (first etching); the size of the preset trench 03 is smaller than the size of the target deep trench 06;

[0095] A preset filling layer 04 is formed in the preset trench 03; the material of the preset filling layer 04 is polycrystalline silicon or oxide.

[0096] An epitaxial layer 05 is formed on a target region of the substrate 01; the target region is the region on the substrate 01 other than the preset filling layer 04.

[0097] The preset filling layer 04 is removed by etching, and the initial trench (second etching) is formed on the epitaxial layer 05 by continuing to etch along the preset trench 03 using a dry etching process; the size of the initial trench is smaller than the size of the target deep trench 06;

[0098] An initial filling layer is formed in the initial trench; the material of the initial filling layer is polycrystalline silicon or oxide.

[0099] An initial epitaxial layer 05 is formed in the unfilled area of ​​the substrate 01; an intermediate trench (third etching) is formed by etching along the initial trench on the initial epitaxial layer 05; the size of the intermediate trench is smaller than the size of the target deep trench 06;

[0100] A filling layer is formed in the intermediate trench, and the target epitaxial layer 05 is formed on the substrate 01.

[0101] The filling layer in the intermediate trench is removed by etching, and the target epitaxial layer 05 is etched (fourth etching) to form the target deep trench 06 on the basis of the intermediate trench.

[0102] The above embodiment is only an exemplary implementation method. In actual application, the number of etching times can be adjusted according to the depth of the target deep groove 06.

[0103] In some embodiments, forming a predetermined trench 03 on the substrate 01 includes:

[0104] Photoresist is coated on the surface of the substrate 01;

[0105] Obtain the target photomask corresponding to the target deep groove 06;

[0106] The photoresist is exposed using the target photomask, and the preset trench 03 is formed on the substrate 01 by adjusting the photolithography conditions;

[0107] The step of continuing to etch along the preset trench 03 on the epitaxial layer 05 to form the target deep trench 06 includes:

[0108] The target photomask is used to continue etching along the preset groove 03 on the epitaxial layer 05 to form the target deep groove 06.

[0109] In the embodiments of this specification, during the trench etching process, only one target photomask can be fabricated. Photoresist can be coated on the surface of the substrate 01 first, and the target photomask can be used to expose the photoresist. By adjusting the photolithography conditions, the preset trench 03 can be formed on the substrate 01. The photolithography conditions may include, but are not limited to, exposure energy, exposure time, mask thickness, and wavelength. During the etching process of the target deep trench 06, the same target photomask can be used, and by further adjusting the photolithography conditions, a similar method can be used to etch the epitaxial layer 05, and the substrate 01 at the bottom of the epitaxial layer 05 can be etched to form the target deep trench 06.

[0110] In the embodiments described in this specification, only one photomask can be used in the multiple etching processes. Therefore, the number of photomasks will not be increased during the etching process of the target deep trench 06.

[0111] In the embodiments described in this specification, the method further includes:

[0112] The polycrystalline silicon or oxide is filled into the target deep trench 06;

[0113] The filling surface of the target deep trench 06 is planarized to form a target filling layer 07; the surface of the target filling layer 07 is flush with the surface of the epitaxial layer 05.

[0114] In the embodiments described in this specification, such as Figure 8 As shown, polysilicon or oxide can be filled into the target deep trench 06; then, the filled surface of the target deep trench 06 is planarized to form a target filling layer 07; the surface of the target filling layer 07 is flush with the surface of the epitaxial layer 05, thereby obtaining a semiconductor structure based on the target deep trench 06. In this semiconductor structure, the depth of the target deep trench 06 is at least 30 micrometers, which can meet the requirement of withstanding 100V high voltage, while also meeting the requirement of an aspect ratio (depth / width) greater than 10, and has good isolation effect. Filling the target deep trench 06 with a non-conductive dielectric, through the physical isolation of the dielectric, achieves the purpose of forming electrical isolation on the silicon wafer, thus improving the electrical isolation effect.

[0115] In one exemplary embodiment, such as Figure 9 As shown, Figure 9 A method for etching a target deep trench, the target deep trench having a depth of 30 micrometers and a width of 2 micrometers; the method includes:

[0116] (1) A preset trench smaller than the target depth is formed on a single crystal silicon substrate; a preset trench with a depth of 10 micrometers and a width of 1 μm is etched out, and polycrystalline silicon is deposited in the preset trench. The deposited layer is then chemically and mechanically polished to form a preset filling layer so that the surface of the preset filling layer is flush with the surface of the substrate.

[0117] (2) Selective epitaxial layer growth is performed on the substrate surface; at this time, the epitaxial layer is grown on the surface of the single crystal silicon substrate, and not on the surface of the preset filling layer (polycrystalline silicon);

[0118] (3) Etch away the preset filling layer (polysilicon) on the substrate;

[0119] (4) Dry etching is performed on the epitaxial layer to form the target deep trench. Since a 10 μm x 1 μm trench already exists, less single-crystal silicon is etched compared to traditional deep trench processes, resulting in a flat bottom morphology for the deep trench. At this time, etching can modify the surface morphology of the target deep trench, deepening and widening it to achieve the depth and width required for high voltage in the device. The depth-to-width ratio of the target deep trench is 30 μm: 2 μm.

[0120] (5) Fill the target deep trench and deposit polycrystalline silicon in the target deep trench;

[0121] (6) The surface morphology of polycrystalline silicon is planarized by chemical mechanical polishing to form a target filling layer; wherein the surface of the target filling layer is flush with the surface of the epitaxial layer.

[0122] In this embodiment, during the etching process of the target deep trench, a small preset trench is first formed on the substrate, a preset filling layer is formed in the preset trench, and then an epitaxial layer is formed on the non-filled area of ​​the substrate. The epitaxial layer distinguishes the deep trench location from other locations. After etching away the preset filling layer, the preset trench is further etched on the epitaxial layer to form the target deep trench. This reduces the difficulty of the etching process of the target deep trench, and the formed target deep trench has steep sidewalls and a flat bottom, which can ensure that the deep trench achieves the required aspect ratio and improves the electrical isolation effect of the deep trench structure.

[0123] The present invention also provides an electronic device, which may include the target deep trench provided in the embodiments of the present invention.

[0124] The electronic device in this embodiment can be any electronic product or device with photoelectric sensing function, such as a mobile phone, tablet computer, laptop computer, navigator, camera, camcorder, robot vacuum cleaner, virtual reality device, augmented reality device, etc., or any intermediate product including the aforementioned photoelectric sensor.

[0125] In the etching process of the target deep trench in this specification embodiment, a small preset trench is first formed on the substrate, a preset filling layer is formed in the preset trench, and then an epitaxial layer is formed on the non-filled area of ​​the substrate. The epitaxial layer distinguishes the deep trench location from other locations. After etching away the preset filling layer, the preset trench is further etched on the epitaxial layer to form the target deep trench. This reduces the difficulty of the etching process of the target deep trench, and the formed target deep trench has steep sidewalls and a flat bottom, which can ensure that the deep trench achieves the required aspect ratio and improves the isolation effect of the deep trench structure.

[0126] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the claims.

[0127] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for etching deep trenches, characterized in that, The method includes: Provide substrate; Pre-defined trenches are formed on the substrate; A preset filling layer is formed in the preset trench; The preset filling layer is planarized to make it flush with the substrate, and an epitaxial layer is formed on the substrate; The preset filler layer is removed by etching, and the target deep trench is formed by continuing to etch along the preset trench on the epitaxial layer.

2. The method according to claim 1, characterized in that, When the depth of the target trench is greater than the target depth, the step of continuing to etch along the preset trench on the epitaxial layer to form the target trench includes: A dry etching process is used to continue etching along the preset trench on the epitaxial layer to form an initial trench; the size of the initial trench is smaller than the size of the target deep trench. The initial trench is used as the current trench, and a current filling layer is formed in the current trench; the material of the current filling layer is polycrystalline silicon or oxide; The current epitaxial layer is formed in the unfilled region of the substrate; The target deep trench is formed by continuing etching along the current trench on the current epitaxial layer.

3. The method according to claim 2, characterized in that, The step of continuing to etch along the current trench on the current epitaxial layer to form the target deep trench includes: Continue etching along the current trench on the current epitaxial layer to form an intermediate trench; When the size of the intermediate trench is smaller than the size of the target deep trench, the intermediate trench is used as the current trench again; Repeat the steps of forming the current fill layer in the current trench to continue etching along the current trench on the current epitaxial layer to form an intermediate trench, until the size of the intermediate trench is the same as the size of the target deep trench.

4. The method according to claim 1, characterized in that, The formation of the epitaxial layer on the substrate includes: The substrate containing the preset filling layer is placed in a cavity at 500-800°C, and a single-crystal silicon epitaxial layer is formed on the target area of ​​the substrate by reacting the epitaxial generation gas with hydrogen; the target area is the area on the substrate other than the preset filling layer.

5. The method according to claim 4, characterized in that, The difference between the thickness of the epitaxial layer and the preset depth is The preset depth is the depth difference between the target deep trench and the preset groove; the epitaxial generated gas includes at least one of silicon tetrachloride and tetrachlorohydrocarbon.

6. The method according to claim 1, characterized in that, The depth of the preset trench is less than the depth of the target deep trench, and the width of the preset trench is less than the width of the target deep trench; the bottom of the target deep trench is flat and the sidewalls are steep.

7. The method according to claim 6, characterized in that, The depth ratio of the preset groove to the target deep groove is (2-3):6, and the width ratio of the preset groove to the target deep groove is (0.5-0.8):

1.

8. The method according to claim 7, characterized in that, The target deep groove has a depth of 30 micrometers, and the preset groove has a depth of 10-15 micrometers; the target deep groove has a width of 2.0 micrometers, and the preset groove has a width of 1.0-1.6 micrometers.

9. The method according to claim 1, characterized in that, The step of forming a preset filling layer in the preset trench includes: The polycrystalline silicon or oxide is filled into the preset trench; The filling surface of the preset trench is planarized to form the preset filling layer; the surface of the preset filling layer is flush with the surface of the substrate.

10. The method according to claim 1, characterized in that, The method further includes: The target deep trench is filled with polycrystalline silicon or oxide; The filling surface of the target deep trench is planarized to form a target filling layer; the surface of the target filling layer is flush with the surface of the epitaxial layer.

11. The method according to claim 1, characterized in that, The process of forming a predetermined trench on the substrate includes: Photoresist is coated on the surface of the substrate; Obtain the target photomask corresponding to the target deep groove; The photoresist is exposed using the target photomask, and the preset trenches are formed on the substrate by adjusting the photolithography conditions; The step of continuing to etch along the preset trench on the epitaxial layer to form the target deep trench includes: The target deep groove is formed by continuing to etch along the preset trench on the epitaxial layer using the target photomask.

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