Manufacturing method of double-depth groove

Abstract

The invention discloses a manufacturing method of a double-depth groove, and belongs to the technical field of semiconductor integrated circuit manufacturing. According to the method, at least two grooves which are the same in depth and different in width are manufactured in a substrate and a hard mask layer, the two grooves are the narrow deep groove and the wide shallow groove respectively, then a first sacrificial layer and a protective layer are manufactured on the hard mask layer in sequence, and in the process, the narrow deep groove is sealed through the first sacrificial layer; when the sealing structure of the narrow and deep groove and the first sacrificial layer in the narrow and deep groove are removed, the protection layer can protect the wide and shallow groove; and further performing depth expansion on the narrow and deep groove to form a target depth, and removing the material in the wide and shallow groove to form a double-depth groove. By adopting the method provided by the invention, the narrow and deep grooves and the wide and shallow grooves with different depths can be simultaneously manufactured by only using one photomask, and the cost of manufacturing the back-illuminated image sensor is obviously reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor integrated circuit manufacturing, and in particular relates to a method for manufacturing a double-depth groove. Background Art

[0002] ‌Back-illuminated image sensor is a specially designed image sensor, which is characterized by light entering from the back of the sensor and directly irradiating the photosensitive device, thereby effectively improving light utilization efficiency and image quality, especially in low-light environments. In order to make the back-illuminated image sensor meet the isolation requirements between the photodiode and the charge storage area, the manufacturing process and product yield of the back-illuminated image sensor, and improve the performance of the back-illuminated image sensor, two different types of grooves need to be formed in the manufacturing process of the back-illuminated image sensor: a narrow and deep narrow deep groove and a wide and shallow wide shallow groove.

[0003] Narrow deep grooves are used to isolate photodiodes to ensure the photoelectric conversion efficiency and signal isolation of back-illuminated image sensors, thereby avoiding mutual interference between signals, which is the basis for ensuring the imaging quality and stable performance of back-illuminated image sensors. Wide shallow grooves are used to arrange metal wires to increase the actual width of the wires, thereby reducing wire resistance and improving circuit performance. Therefore, narrow deep grooves and wide shallow grooves are important structural components of back-illuminated image sensors.

[0004] In the process of making narrow deep grooves and wide shallow grooves, a mask is needed. The mask (also called a photomask or photolithography mask) is used as a template in the process of manufacturing back-illuminated image sensors to form a circuit pattern by controlling the transmission of light. Due to the different sizes of narrow deep grooves and wide shallow grooves, two masks are needed to make the two types of grooves respectively during the production process, resulting in higher production costs. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for manufacturing a double-depth groove to solve the problem in the prior art that in the process of manufacturing a back-illuminated image sensor, two masks are required due to the presence of grooves of two depths and widths, resulting in high production costs.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for manufacturing a double-depth groove comprises the following steps: forming a hard mask layer on the substrate; At least two trenches of the same depth are made in the substrate and the hard mask layer, which are a first process narrow deep trench and a first process wide shallow trench; on the same plane, the cross-sectional area of ​​the first process narrow deep trench is smaller than the cross-sectional area of ​​the first process wide shallow trench; A first sacrificial layer is formed on the surface of the first process narrow deep groove and the surface of the first process wide shallow groove to form a second process narrow deep groove and a second process wide shallow groove; the upper end of the second process narrow deep groove is a sealing structure, and the inside is a cavity; Forming a protection layer on the first sacrificial layer, wherein the protection layer covers the inner sidewall of the second process wide shallow trench; Removing part of the hard mask layer, the sealing structure is removed, and the upper end of the second process narrow deep trench is opened; Removing the first sacrificial layer in the second process narrow and deep trench, processing the second process narrow and deep trench to the depth of the target narrow and deep trench, and removing the protective layer in the second process wide and shallow trench; After removing the remaining hard mask layer, a target narrow deep trench and a target wide shallow trench are formed.

[0007] A further improvement of the present invention is: Preferably, the depth of the grooves of the same depth is equal to the depth of the target wide and shallow grooves.

[0008] Preferably, the first sacrificial layer is a silicon oxide layer, and the protective layer is a silicon oxynitride layer.

[0009] Preferably, the first sacrificial layer includes a silicon oxide layer and a polysilicon layer, and the protective layer is a silicon oxide layer.

[0010] Preferably, the protective layer is obtained by converting a partial thickness of the first sacrificial layer.

[0011] Preferably, the upper end of the cavity is higher than the upper surface of the substrate.

[0012] Preferably, before removing part of the hard mask layer, a second sacrificial layer is formed on the protective layer, and the second process wide shallow trench is filled with the second sacrificial layer material.

[0013] Preferably, the second sacrificial layer is a silicon oxide layer or a silicon nitride layer.

[0014] Preferably, after removing part of the hard mask layer, the second process narrow deep trench becomes the third process narrow deep trench, and the second process wide shallow trench becomes the third process wide shallow trench; After the first sacrificial layer in the third process narrow and deep trench is removed, a fourth process narrow and deep trench is formed, and the third process wide and shallow trench becomes a fourth process wide and shallow trench.

[0015] Preferably, the depth of the narrow and deep groove of the fourth process is processed to the depth of the target narrow and deep groove to obtain the target narrow and deep groove; The second sacrificial layer and the protective layer in the wide and shallow trench of the fourth process are removed to obtain the target wide and shallow trench.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for manufacturing a double-depth groove, wherein the method firstly manufactures a first-process narrow deep groove and a first-process wide shallow groove of the same depth in a substrate and a hard mask layer through a photomask, seals the upper end of the first-process narrow deep groove through a first sacrificial layer, and then manufactures a protective layer and a second sacrificial layer on the first sacrificial layer in sequence, wherein the protective layer can protect the sidewall of the active area adjacent to the wide shallow groove from being exposed when the first sacrificial layer in the second-process narrow deep groove is removed. By adopting the method of the present invention, only one photomask can be used to simultaneously manufacture target narrow deep grooves and target wide shallow grooves that meet the requirements, significantly reducing the manufacturing cost. In addition, the method also has the advantages of simple process and easy implementation, and is suitable for large-scale industrial production. The double-depth groove structure can be used to manufacture back-illuminated image sensors, which helps to improve the performance of back-illuminated image sensors and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of a method for manufacturing a dual-depth groove sensor of the present invention; Figure 2 A schematic diagram of the structure of manufacturing a hard mask layer on a substrate according to the present invention; Figure 3 A schematic diagram of the structure of making a first process narrow deep groove and a first process wide shallow groove of the present invention; Figure 4 It is a structural schematic diagram of manufacturing a first sacrificial layer on a hard mask layer according to the present invention; Figure 5 This is a schematic diagram of the structure of manufacturing a protective layer on the first sacrificial layer according to the present invention; Figure 6 It is a structural schematic diagram of manufacturing a second sacrificial layer on a protective layer according to the present invention; Figure 7 A schematic diagram of the structure of the present invention in which a portion of the hard mask layer is removed; Figure 8 A schematic diagram of the structure of removing the first sacrificial layer inside the narrow and deep trench in the third process of the present invention; Fig. 9 It is a schematic structural diagram of the fourth process narrow and deep groove being transformed into the target narrow and deep groove in the present invention; Fig.10 It is a schematic diagram of the structure of converting the fourth process wide shallow groove into the target wide shallow groove of the present invention; Fig.11 It is a schematic diagram of the structure of the double-depth trench after removing the hard mask layer of the present invention; Among them: 1. substrate; 2. hard mask layer; 3. first sacrificial layer; 4. protective layer; 5. second sacrificial layer; 301. sealing structure; 601. first process narrow and deep groove; 602. second process narrow and deep groove; 603. third process narrow and deep groove; 604. fourth process narrow and deep groove; 605. target narrow and deep groove; 701. first process wide and shallow groove; 702. second process wide and shallow groove; 703. third process wide and shallow groove; 704. fourth process wide and shallow groove; 705. target wide and shallow groove. DETAILED DESCRIPTION

[0018] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0019] Back-illuminated image sensors improve light utilization efficiency and image quality by allowing light to enter from the back and directly illuminate the photosensitive device. During its manufacturing process, it is necessary to form narrow and deep grooves for isolating photodiodes, and wide and shallow grooves for arranging metal wires to reduce resistance; narrow and deep grooves are narrow and deep grooves in size, and wide and shallow grooves are wide and shallow grooves in size. A more specific structural description is that the cross-sectional area of ​​the narrow and deep groove on the same plane is smaller than the cross-sectional area of ​​the wide and shallow groove, and the depth of the narrow and deep groove is greater than the depth of the wide and shallow groove. Due to the different sizes of these two grooves, they are traditionally made using two masks, which increases the production cost.

[0020] In view of the above problems, the present invention discloses a solution, which is to first form grooves of the same depth but different widths on the hard mask layer and the substrate, which are respectively a process narrow deep groove and a process wide shallow groove, and form a sacrificial layer on the surface of the grooves. At the same time, the sacrificial layer seals the upper end of the narrow deep groove to form a sealing structure, and further form a protective layer on the sacrificial layer, and then remove it together with the sealing structure, so that the upper end of the process narrow deep groove is exposed. At this time, there is still a protective layer on the surface of the process wide shallow groove, so that when the sacrificial layer on the surface of the process narrow deep groove is removed, the protective layer can protect the side wall of the active area adjacent to the process wide shallow groove from being damaged and exposed; further remove the sacrificial layer in the narrow deep groove, and at the same time, etch the narrow deep groove to the target depth. This method enables only one mask to form multiple grooves with two target sizes.

[0021] See also Figure 1 The present invention discloses a method for manufacturing a double-depth groove, which comprises the following steps: S1, forming a hard mask layer 2 on a substrate 1; S2, placing a photomask on the hard mask layer 2, and making at least two grooves of the same depth in the substrate 1 and the hard mask layer 2, namely a first process narrow deep groove 601 and a first process wide shallow groove 701; on the same plane, the cross-sectional area of ​​the first process narrow deep groove 601 is smaller than the cross-sectional area of ​​the first process wide shallow groove 701; S3, forming a first sacrificial layer 3 on the surface of the first process narrow deep groove 601 and the first process wide shallow groove 701, forming a second process narrow deep groove 602 and a second process wide shallow groove 702; the upper end surface of the second process narrow deep groove 602 is a sealing structure 301, and the interior is a cavity; S4, forming a protection layer 4 on the first sacrificial layer 3, wherein the protection layer 4 covers the inner sidewall of the second process wide shallow trench 702; S5, removing part of the hard mask layer 2, the sealing structure 301 is removed, and the upper end of the second process narrow deep trench 602 is opened; S6, removing the first sacrificial layer 3 in the second process narrow and deep groove 602, processing the second process narrow and deep groove 602 to the depth of the target narrow and deep groove 605, and removing the protective layer 4 in the second process wide and shallow groove 702; S7 , after removing the remaining hard mask layer 2 , a target narrow deep trench 605 and a target wide shallow trench 705 are formed.

[0022] The following will be combined Figure 2~Figure 9 Let's introduce it in detail Figure 1 The method for manufacturing a double-depth groove provided in some embodiments of the present invention is shown as follows: Figure 2~Figure 9 It is a schematic structural diagram of the manufacturing process of the double-depth groove manufacturing method provided in some embodiments of the present invention.

[0023] See also Figure 2 In S1, a substrate 1 is provided first, which is used as a platform for subsequently forming narrow deep grooves and wide shallow grooves. A hard mask layer 2 is formed on the substrate 1. The hard mask layer 2 is an inorganic thin film material, mainly composed of a series of inorganic compounds, such as silicon oxynitride, silicon oxide or amorphous carbon. As an intermediate medium, the hard mask layer 2 can accurately transfer the pattern formed in the photolithography process to the target material, which is particularly suitable for situations where high-precision pattern transfer is required.

[0024] Furthermore, when the hard mask layer 2 is formed on the substrate 1, chemical vapor deposition (CVD) or physical vapor deposition (PVD) is used. These methods can directly deposit the required thin film material from gas molecules through chemical reactions at high temperatures. In addition, plasma enhanced chemical vapor deposition (PECVD) can be used to further improve the deposition rate and film quality.

[0025] It should be understood that the hard mask layer 2 is used in the process of forming the trenches. After the required double-depth trenches are formed, the hard mask layer 2 needs to be removed and will not be retained in the final back-illuminated image sensor.

[0026] It should be understood that the substrate 1 in the present invention can be any suitable material well known in the art as a substrate. For example, it can be composed of one or more of the following materials: silicon (Si), germanium (Ge), germanium silicon alloy (SiGe), carbon silicon alloy (SiC), carbon germanium silicon alloy (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), and also includes a multilayer composite structure composed of these semiconductor materials. In addition, it can also be a double-sided polished silicon wafer (DSP), an alumina ceramic substrate, a quartz substrate or a glass substrate. Specifically, in the embodiment of the present invention, the substrate 1 is exemplified by a silicon wafer as the substrate 1.

[0027] See also Figure 3 In S2, on the hard mask layer 2 and the substrate 1, a photomask is placed on the hard mask layer 2, and at least two grooves of the same depth are made by etching, namely the first process narrow deep groove 601 and the first process wide shallow groove 701, which are used to prepare for the final grooves of different depths. In the process of making grooves of the same depth, the specific number and arrangement are determined according to specific process requirements. In this step, the grooves with different final depths are first made into process grooves with the same depth, which can avoid the use of two photomasks.

[0028] In some embodiments of the present invention, the depth of the first process narrow deep groove 601 and the first process wide shallow groove 701 is less than or equal to the depth of the target wide shallow groove 705, leaving a processing margin for subsequent further processing to form the final target narrow deep groove 605 and the target wide shallow groove 705. More preferably, the depth of the first process narrow deep groove 601 and the first process wide shallow groove 701 made in this step is the same as the depth of the final target wide shallow groove 705, so that in the subsequent processing, only the first process narrow deep groove 601 needs to be further processed, and there is no need to further process and improve the depth of the process wide shallow groove, thereby simplifying the process.

[0029] Furthermore, the first-process narrow deep trench 601 and the first-process wide shallow trench 701 are formed by a plasma etching method.

[0030] Furthermore, the width of the narrow deep groove 601 of the first process is equal to the width of the target narrow deep groove 605 finally produced, and the width of the wide shallow groove 701 of the first process is equal to the width of the target wide shallow groove 705 finally produced, so that the subsequent processing process only needs to further etch the depth of the groove without adjusting the width.

[0031] In the embodiment of the present invention, in order to simplify the description, the subsequent descriptions and drawings all use a narrow deep groove and a wide shallow groove as illustrations.

[0032] See also Figure 4 In S3, a first sacrificial layer 3 is deposited on the upper surface of the hard mask layer 2, and the inner surfaces of the first process narrow deep groove 601 and the first process wide shallow groove 701 are covered by the first sacrificial layer 3. At the same time, the upper end of the first process narrow deep groove 601 is covered and sealed by the material of the first sacrificial layer 3 to form a second process narrow deep groove 602 and a second process wide shallow groove 702. The upper end of the second process narrow deep groove 602 is a sealing structure 301, and the interior is a cavity.

[0033] It should be understood that the height of the cavity is greater than the height of the upper surface of the substrate 1 , so as to ensure that the sealing structure 301 will not remain when the upper sealing structure 301 is subsequently removed.

[0034] It should be noted that the first sacrificial layer 3 has two main functions. One is to seal the upper end surface of the narrow and deep groove 601 of the first process so that it is not affected when the protective layer 4 is formed later. The inner surface of the narrow and deep groove 602 of the second process is only covered by the first sacrificial layer 3, reducing the complexity of the subsequent removal of the internal material of the narrow and deep groove 603 of the third process; the other function is to prepare for the subsequent protective layer 4.

[0035] In some embodiments of the present invention, the first sacrificial layer 3 is made of silicon oxide, which can be manufactured by conventional processes and easily removed by subsequent etching methods, thus facilitating the entire process.

[0036] Furthermore, silicon oxide is deposited by high density plasma (HDP), and only deposition is performed without etching in this process to form a sealing structure 301, and the filling is stopped after the top of the first process narrow deep trench 601 is completely sealed.

[0037] See also Figure 4 , S3, in some other embodiments of the present invention, the first sacrificial layer 3 adopts a composite film of silicon oxide and polysilicon, wherein the thickness of the polysilicon layer is much greater than the thickness of the silicon oxide layer. During the manufacturing process, a silicon oxide film layer is first deposited with a thickness of 2nm~5nm, which is used to isolate the substrate 1 and the subsequently deposited polysilicon layer. The thickness of the polysilicon layer must ensure that a sealing structure 301 can be formed at the upper end of the first process narrow and deep trench 601, and the thickness is tens or hundreds of times that of the silicon oxide film layer. Then, a polysilicon layer is deposited by a high-density plasma method, and only deposition is performed in this process without etching to form a sealing structure 301. At this time, the inner sidewall of the first process narrow and deep trench 601 is covered by a very thin silicon oxide film layer, and there is a polysilicon layer outside the silicon oxide film layer.

[0038] See also Figure 5 In S4, a protective layer 4 is formed on the upper surface of the first sacrificial layer 3, and the protective layer 4 covers the upper surface of the entire first sacrificial layer 3, and at the same time covers the surface of the first sacrificial layer 3 inside the second process wide shallow groove 702. The protective layer 4 is mainly used to protect the inner surface of the third process wide shallow groove 703 from being affected when the first sacrificial layer 3 inside the third process narrow deep groove 603 is subsequently removed and the depth of the fourth process narrow deep groove 604 is deepened.

[0039] See also Figure 5In some embodiments of the present invention, on the basis of the first sacrificial layer 3 being made of silicon oxide, the protective layer 4 is made of a silicon oxynitride layer, which is obtained by plasma nitriding the first sacrificial layer 3 made of silicon oxide. In this step, a part of the first sacrificial layer 3 is directly transformed into the protective layer 4, and the protective layer 4 causes the covering material of the sidewall of the second-process wide shallow trench 702 to be transformed from the first sacrificial layer 3 to the protective layer 4 of the new material, while the covering material of the sidewall of the second-process narrow deep trench 602 remains the first sacrificial layer 3. That is, the covering material on the sidewall of the second-process wide shallow trench 702 is no longer the same as the covering material on the sidewall of the second-process narrow deep trench 602. In this way, when the sidewall covering layer (i.e., the first sacrificial layer 3) of the third-process narrow deep trench 603 is subsequently removed, the sidewall covering layer (i.e., the protective layer 4) of the third-process wide shallow trench 703 is not affected, so that the sidewall of the active area adjacent to the third-process wide shallow trench 703 can be well protected from being exposed. At the same time, in the process of deepening the fourth process narrow deep trench 604 and forming the fourth process wide shallow trench 704, the active area adjacent to the fourth process wide shallow trench 704 will not be damaged.

[0040] Furthermore, in this step, as a preferred method, the process parameters of the plasma nitridation treatment are such that the first sacrificial layer 3 inside the second process wide shallow trench 702 is completely transformed into the protective layer 4 in the thickness direction, so that the thickness of the protective layer 4 can provide sufficient protection for the active area in subsequent processes.

[0041] Furthermore, in this step, as a preferred method, when the first sacrificial layer 3 is a composite film of silicon oxide and polysilicon, at this time in S4, a portion of the polysilicon layer can be oxidized to form a protective layer 4, and the material of the protective layer 4 is silicon oxide.

[0042] See also Figure 6 In some embodiments of the present invention, a second sacrificial layer 5 is formed on the protective layer 4 , and the second sacrificial layer 5 completely covers the upper surface of the protective layer 4 and completely fills the interior of the second process wide shallow trench 702 .

[0043] Furthermore, on the basis that the protective layer 4 is silicon oxynitride, the second sacrificial layer 5 is a silicon oxide layer. Since the second sacrificial layer 5 is mainly filled in the second process wide shallow groove 702, and the interior of the second process wide shallow groove 702 is a recessed structure, when manufacturing the second sacrificial layer 5, a spin on glass coating method (SOG) is selected.

[0044] In some embodiments, on the basis that the protection layer 4 is made of silicon oxide, the material of the second sacrificial layer 5 can be silicon nitride.

[0045] In a specific embodiment of the present invention, Figure 6In the embodiment, stacked in sequence on the hard mask layer 2 are a first sacrificial layer 3 made of silicon oxide, a protective layer 4 made of silicon oxynitride, and a second sacrificial layer 5 made of silicon oxide.

[0046] In a specific embodiment of the present invention, Figure 6 In the figure, stacked in sequence above the hard mask layer 2 are a first sacrificial layer 3 made of silicon oxide and polysilicon, a protective layer 4 made of silicon oxide, and a second sacrificial layer 5 made of silicon nitride; wherein, in the first sacrificial layer 3, the silicon oxide is below or inside the polysilicon.

[0047] See also Figure 7 In S5, the upper part of the hard mask layer 2 is removed, so that the sealing structure 301 at the upper end of the second process narrow deep groove 602 is removed to form a third process narrow deep groove 603, and a part of the second process wide shallow groove 702 is removed to form a third process wide shallow groove 703; the depth of the third process narrow deep groove 603 is equal to the depth of the target wide shallow groove 705, and there is only the first sacrificial layer 3 on the inner surface, and the depth of the third process wide shallow groove 703 is the same as the depth of the target wide shallow groove 705; the inner surface of the third process wide shallow groove 703 is covered by the protective layer 4, and the third process wide shallow groove 703 is filled with the second sacrificial layer 5, and the second sacrificial layer 5 is surrounded by the protective layer 4.

[0048] It should be understood that in this process, it is necessary to enable the sealing structure 301 to be completely removed, the upper surface of the third-process wide shallow groove 703 is cut into a plane, and the second sacrificial layer 5 completely fills the interior of the third-process wide shallow groove 703. This structure enables the second sacrificial layer 5 to fully protect the side walls of the inner surface of the third-process wide shallow groove 703 and the adjacent active area from being affected during the subsequent deepening of the narrow and deep groove.

[0049] Preferably, the process processes the hard mask layer 2, the first sacrificial layer 3 in the second process narrow and deep groove 602, the protective layer 4 and the second sacrificial layer 5 in the second process wide and shallow groove 702 by chemical mechanical polishing (CMP). After the process, the upper surface of the entire hard mask layer 2 and the internal structure is flat.

[0050] In some embodiments of the present invention, each sacrificial layer and the protective layer 4 are subsequently removed by a selective etching method, so that when a certain layer is etched and removed, other layers will not be affected.

[0051] See also Figure 8In S6, the first sacrificial layer 3 in the third process narrow and deep groove 603 is removed to form a fourth process narrow and deep groove 604; at the same time, the third process wide and shallow groove 703 may be affected during the removal process, and a portion of the second sacrificial layer 5 is removed. However, under the action of the protective layer 4, the side wall of the third process wide and shallow groove 703 can be avoided from being affected, and the third process wide and shallow groove 703 is transformed into the fourth process wide and shallow groove 704.

[0052] In some embodiments, when the material of the first sacrificial layer 3 is silicon oxide, it is removed by wet etching with a hydrofluoric acid solution in the process. When the material of the first sacrificial layer 3 is silicon oxide and polysilicon, the polysilicon is removed by etching with tetramethylammonium hydroxide, and the silicon oxide is removed by wet etching with a hydrofluoric acid solution. Exemplarily, the hydrofluoric acid solution is a mixed solution of hydrofluoric acid and water, wherein the volume ratio of hydrofluoric acid to water is 1:200.

[0053] In some embodiments, the first sacrificial layer 3 and the second sacrificial layer 5 are both silicon oxide, and the protective layer 4 is a silicon oxynitride layer. Therefore, when the first sacrificial layer 3 is removed by wet etching with a hydrofluoric acid solution, a portion of the second sacrificial layer 5 will be removed, but the silicon oxynitride layer serving as the protective layer 4 will not be corroded and removed. At this time, the upper end of the fourth-process wide shallow trench 704 formed is step-shaped, and the protective layer 4 can protect the side wall of the active area of ​​the fourth-process wide shallow trench 704.

[0054] In some embodiments, the first sacrificial layer 3 is silicon oxide and polysilicon, the protective layer 4 is silicon oxide, and the second sacrificial layer 5 is silicon nitride. When removing the polysilicon, there is basically no effect on the protective layer 4 and the second sacrificial layer 5. When removing the silicon oxide in the first sacrificial layer 3, since the silicon oxide layer in the first sacrificial layer 3 is very thin, there is almost no effect on the protective layer 4 with a thickness of about tens of nanometers. At this time, the shape and size of the fourth process wide shallow trench 704 are basically consistent with the third process wide shallow trench 703.

[0055] See also Fig. 9 In S6, the fourth process narrow deep groove 604 is further etched by plasma etching, so as to form a deeper groove in the fourth process narrow deep groove 604, reach the target depth, and form the final target narrow deep groove 605. In this process, under the effect of the protective layer 4, the sidewall of the fourth process wide shallow groove 704 is still not affected.

[0056] See also Fig.10 In S6, the second sacrificial layer 5 and the protective layer 4 inside the fourth process wide shallow trench 704 are removed.

[0057] In some embodiments, when the protective layer 4 is a silicon oxynitride layer, the specific removal method can be to first use a hydrofluoric acid solution to remove the second sacrificial layer 5 whose material is silicon oxide, and then use a hot phosphoric acid solution to remove the protective layer 4 whose material is silicon oxynitride. Exemplarily, in the hydrofluoric acid, the volume ratio of hydrofluoric acid to water is 1:200, and the phosphoric acid solution is a mixed solution composed of phosphoric acid and water, wherein the concentration of the phosphoric acid solution is 85%.

[0058] In some embodiments, when the protective layer 4 is silicon oxide, firstly, 85% phosphoric acid solution is used to remove the second sacrificial layer 5 made of silicon nitride, and then hydrofluoric acid solution is used to remove the protective layer 4 in the fourth process narrow and deep trench 604 .

[0059] See also Fig.11 In S7, in the process of forming the target narrow deep trench 605 and the target wide shallow trench 705 after removing the remaining hard mask layer 2, different methods need to be adopted according to the different components of the hard mask layer 2, such as silicon oxynitride can be removed by phosphoric acid solution, and silicon oxide can be removed by hydrofluoric acid solution.

[0060] By adopting the above method, only one photomask is needed to simultaneously produce narrow deep grooves and wide shallow grooves, and the semiconductor with the groove structure can be used to produce back-illuminated image sensors.

[0061] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more. In the description of the present invention, the first feature "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features not being in direct contact but being in contact through another feature between them.

[0062] In the description of the present invention, “on”, “over” and “above” a first feature from a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature.

[0063] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0065] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for making a double-depth groove, characterized in that: The following steps are involved: forming a hard mask layer on the substrate; At least two trenches of the same depth are made in the substrate and the hard mask layer, which are a first process narrow deep trench and a first process wide shallow trench; on the same plane, the cross-sectional area of ​​the first process narrow deep trench is smaller than the cross-sectional area of ​​the first process wide shallow trench; A first sacrificial layer is formed on the surface of the first process narrow deep groove and the surface of the first process wide shallow groove to form a second process narrow deep groove and a second process wide shallow groove; the upper end of the second process narrow deep groove is a sealing structure, and the inside is a cavity; Forming a protection layer on the first sacrificial layer, wherein the protection layer covers the inner sidewall of the second process wide shallow trench; Removing part of the hard mask layer, the sealing structure is removed, and the upper end of the second process narrow deep trench is opened; Removing the first sacrificial layer in the second process narrow and deep trench, processing the second process narrow and deep trench to the depth of the target narrow and deep trench, and removing the protective layer in the second process wide and shallow trench; After removing the remaining hard mask layer, a target narrow deep trench and a target wide shallow trench are formed.

2. A method for manufacturing a double-depth groove according to claim 1, characterized in that: The depth of the grooves of the same depth is equal to the depth of the target wide shallow grooves.

3. The method for manufacturing a double-depth groove according to claim 1, characterized in that: The first sacrificial layer is a silicon oxide layer, and the protective layer is a silicon oxynitride layer.

4. The method for manufacturing a double-depth groove according to claim 1, characterized in that: The first sacrificial layer includes a silicon oxide layer and a polysilicon layer, and the protective layer is a silicon oxide layer.

5. A method for manufacturing a double-depth groove according to claim 3 or 4, characterized in that: The protective layer is obtained by converting a first sacrificial layer of partial thickness.

6. The method for manufacturing a double-depth groove according to claim 1, characterized in that: The upper end of the cavity is higher than the upper surface of the substrate.

7. The method for manufacturing a double-depth groove according to claim 1, characterized in that: Before removing part of the hard mask layer, a second sacrificial layer is formed on the protective layer, and the second process wide shallow trench is filled with the second sacrificial layer material.

8. The method for manufacturing a double-depth groove according to claim 7, characterized in that: The second sacrificial layer is a silicon oxide layer or a silicon nitride layer.

9. The method for manufacturing a double-depth groove according to claim 7, characterized in that: After removing part of the hard mask layer, the second process narrow deep trench becomes the third process narrow deep trench, and the second process wide shallow trench becomes the third process wide shallow trench; After the first sacrificial layer in the third process narrow and deep trench is removed, a fourth process narrow and deep trench is formed, and the third process wide and shallow trench becomes a fourth process wide and shallow trench.

10. The method for manufacturing a double-depth groove according to claim 9, characterized in that: Processing the fourth process narrow and deep groove to a depth of a target narrow and deep groove to obtain a target narrow and deep groove; The second sacrificial layer and the protective layer in the wide and shallow trench of the fourth process are removed to obtain the target wide and shallow trench.

Images