Semiconductor structure and preparation method thereof
Through the combined etching process of hydrofluoric acid and M2 etching liquid, the problem of etching inequality of aluminum layer is solved, a stable aluminum layer structure is formed, and the performance and stability of microelectronic devices are improved. It is suitable for devices such as MEMS sensors.
Patent Information
- Application Number
- CN202510432040.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2025-07-11
AI Technical Summary
In the existing microelectronics manufacturing process, the aluminum layer etching process is difficult to ensure etch uniformity, resulting in the bending of the side wall of the through hole and the surface of the aluminum layer, affecting the device performance and long-term stability.
The aluminum layer is etched in sequence using hydrofluoric acid and M2 etching liquid to form a first groove and a second groove, to control the etching angle and depth, reduce the bending and protrusion of the side wall, and control the etching rate and uniformity through the wet etching method.
The uniformity and controllability of aluminum layer etching are achieved, the generation of raised structures is avoided, the overall performance and long-term stability of the device are improved, and it is suitable for devices such as MEMS sensors.
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Figure CN120299995A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of microelectronic manufacturing technology, and particularly to a semiconductor structure and a method for preparing the same. Background Art
[0002] Aluminum (Al), as a metal with light weight and excellent electrical conductivity, is widely used in the field of microelectronic manufacturing to form circuit interconnect layers. Its good electrical conductivity and compatibility with various materials make the aluminum layer a key component for constructing complex electronic structures. Especially in the manufacturing process of integrated circuits, the aluminum layer plays a crucial role.
[0003] In the existing manufacturing process of microelectronic semiconductor structures, in order to construct via holes in the circuit, a combination of photolithography and etching is often used to process the aluminum layer. The photolithography step defines the pattern of the area to be etched by precisely controlling the reaction of light irradiation and photoresist. Subsequently, wet etching technology is used to selectively remove the unprotected part of the aluminum layer by the photoresist, thereby forming the required pattern on the aluminum layer. This process is a key step for realizing circuit interconnection and constructing complex circuit layouts.
[0004] Therefore, how to optimize the aluminum layer etching process to ensure the overall performance and long-term stability of microelectronic devices formed using this semiconductor structure is a technical problem that urgently needs to be solved at present. Summary of the Invention
[0005] In view of the above problems, the present invention is proposed to provide a semiconductor structure and a method for preparing the same that can overcome or at least partially solve the above problems. By sequentially etching the aluminum layer with hydrofluoric acid and M2 etching solution to form the required pattern, the bending degree of the via hole sidewall and the sharp protrusions on the aluminum layer surface can be reduced, thereby ensuring the overall performance and long-term stability of microelectronic devices formed using this semiconductor structure, which is a technical problem that urgently needs to be solved at present.
[0006] In a first aspect, a method for preparing a semiconductor structure is provided, including:
[0007] Providing a semiconductor substrate, on the surface of which there is an aluminum layer;
[0008] Forming a patterned photoresist layer on the aluminum layer, and there are a plurality of etching windows on the photoresist layer;
[0009] Using a first etching solution, perform a first etching on the aluminum layer through the etching window to etch a first groove on the aluminum layer. The side wall of the first groove is an inclined surface, and the included angle between the side wall of the groove and the surface of the aluminum layer away from the semiconductor substrate is a first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the first groove is less than the thickness of the aluminum layer; the first etching solution contains hydrofluoric acid;
[0010] Using a second etching solution, perform a second etching on the aluminum layer formed with the first groove through the etching window to etch a second groove on the aluminum layer. The side wall of the second groove is an inclined surface, the included angle between the side wall of the second groove and the surface of the aluminum layer away from the semiconductor substrate is a second included angle, and the second included angle is less than the first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the second groove is greater than or equal to the thickness of the aluminum layer; the second etching solution is an aluminum etchant;
[0011] Remove the photoresist layer.
[0012] Optionally, the mass fraction of hydrofluoric acid in the first etching solution is 0.10% - 0.25%.
[0013] Optionally, the step of using a first etching solution to perform a first etching on the aluminum layer through the etching window to etch a first groove on the aluminum layer includes:
[0014] Adopt the slot wet etching method, immerse the semiconductor substrate into a first etching tank filled with the first etching solution, and etch the aluminum layer exposed to the etching window to form the first groove on the aluminum layer.
[0015] Optionally, the depth of the first groove is less than or equal to 1 / 2 of the thickness of the aluminum layer.
[0016] Optionally, the step of using a second etching solution to perform a second etching on the aluminum layer formed with the first groove through the etching window to etch a second groove on the aluminum layer includes:
[0017] Adopt the slot wet etching method, immerse the semiconductor substrate into a second etching tank filled with the second etching solution, and etch the aluminum layer formed with the first groove exposed to the etching window to form the second groove on the aluminum layer.
[0018] Optionally, the etching temperature in the second etching tank is 30°C - 40°C.
[0019] Optionally, the aluminum etchant contains phosphoric acid, nitric acid and acetic acid, and the volume ratio of the phosphoric acid, the nitric acid and the acetic acid is 70:2:12.
[0020] Optionally, both the first included angle and the second included angle are obtuse angles, and the second included angle is greater than 120°.
[0021] Optionally, after removing the photoresist layer, the method further includes:
[0022] Forming an insulating layer on the aluminum layer having the second groove.
[0023] In a second aspect, a semiconductor structure is provided, which is prepared by using the preparation method described in the first aspect. The semiconductor structure includes:
[0024] A semiconductor substrate;
[0025] An aluminum layer disposed on one side of the semiconductor substrate. A second groove is formed on the aluminum layer, and the side wall of the second groove is an inclined plane.
[0026] The technical solution provided in the embodiments of the present invention has at least the following technical effects or advantages:
[0027] A semiconductor structure and a preparation method thereof provided in the embodiments of the present invention perform a pretreatment etching by using a first etching solution containing hydrofluoric acid (HF) to form a first groove on the aluminum layer. Among them, hydrofluoric acid can reduce the adhesion between the photoresist and the aluminum layer, promote the acceleration of the etching rate of the aluminum layer and the improvement of the uniformity, so that the side wall of the formed first groove is a plane, which is equivalent to pre-forming a small-angle window with a flat slope on the aluminum layer. The formation of this small-angle window provides a more gentle starting etching surface for the secondary etching, thereby ensuring the uniformity and controllability of the secondary etching process, effectively avoiding the generation of convex structures on the surface of the aluminum layer during the subsequent secondary etching with the second etching solution, and making the side wall of the finally formed second groove present a stable small-angle straight slope shape, with a flat slope and no protrusions. This precisely controlled etching morphology effectively avoids the problem of cracks in the deposited layer caused by too rapid angle change when depositing other material layers on the aluminum layer, meets the high requirements for the stability of the etching angle of devices with special functional requirements, and significantly improves the overall performance and long-term stability of the devices.
[0028] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description. And in order to make the above and other objects, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention are specifically exemplified below. Description of the Drawings
[0029] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present invention. Also, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:
[0030] Figure 1 is a flowchart of a method for fabricating a semiconductor structure provided by the related art;
[0031] Figure 2 is a schematic diagram of a semiconductor structure provided by the related art;
[0032] Figure 3 is a schematic diagram of a FIB image of a partial slice of a semiconductor structure provided by the related art;
[0033] Figure 4 is a flowchart of a method for fabricating a semiconductor structure provided by an embodiment of the present invention;
[0034] Figure 5 is a schematic diagram of a semiconductor substrate provided in step S210;
[0035] Figure 6 is a schematic diagram of the semiconductor substrate after performing step S220;
[0036] Figure 7 is a schematic diagram of the semiconductor substrate after performing step S230;
[0037] Figure 8 is a schematic diagram of a FIB image of a partial slice of a semiconductor structure provided by an embodiment of the present invention;
[0038] Figure 9 is a schematic diagram of the semiconductor substrate after performing step S240;
[0039] Figure 10 is a schematic diagram of a FIB image of a partial slice of another semiconductor structure provided by an embodiment of the present invention;
[0040] Figure 11 is a schematic diagram of a semiconductor structure provided by an embodiment of the present invention. Detailed Embodiments
[0041] To better understand the above technical solutions, the following will combine the accompanying drawings of the specification and specific embodiments to elaborate on the above technical solutions in detail. It should be understood that the embodiments of the present disclosure and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, rather than limitations on the technical solutions of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.
[0042] To better understand the present invention, a preparation method of a semiconductor structure provided in the related art is briefly described below:
[0043] Figure 1 is a flowchart of a preparation method of a semiconductor structure provided in the related art. As Figure 1 shown, the preparation method includes:
[0044] Step S110: Provide a semiconductor substrate with an aluminum layer on its surface.
[0045] Step S120: Form a patterned photoresist layer on the aluminum layer, and there are a plurality of etching windows on the photoresist layer.
[0046] Step S130: Use an aluminum etchant to etch the aluminum layer through the etching windows to etch and form a desired pattern on the aluminum layer.
[0047] Step S140: Remove the photoresist layer.
[0048] The above preparation method uses an aluminum etchant to perform wet etching on the aluminum layer to form a desired pattern on the aluminum layer. However, the inventor found in the research that wet etching exhibits isotropic characteristics and cannot control the etching uniformity in each direction of the aluminum layer. In addition, the contact between the photoresist and the aluminum layer will also cause the etching rate to slow down, resulting in an extremely curved shape of the side wall of the through hole formed by etching, and sharp convex structures are likely to form on the surface of the aluminum layer. After the photoresist is removed, the convex structures still exist. For products with special requirements, when an insulating layer (such as silicon nitride or silicon oxide) needs to be deposited on the aluminum layer subsequently, the convex parts of the aluminum layer may cause cracks at the interface of the insulating layer, which not only affects the overall performance of the product but also may significantly reduce its long-term stability.
[0049] Figure 2 is a schematic diagram of a semiconductor structure provided in the related art. As Figure 2 shown, the semiconductor structure 100 is prepared by using the preparation method as Figure 1 shown. The semiconductor structure includes a substrate 11 and an aluminum layer 12 located above the substrate 11. A groove 12a is etched on the aluminum layer 12, and the side wall of the groove 12a is in a curved shape. Through the Focused Ion Beam (FIB) technology, the FIB imaging of the semiconductor structure can be obtained. Figure 3 is a schematic diagram of the FIB imaging of a partial slice of a semiconductor structure provided in the related art. Figure 3 The shown slice imaging is the slice imaging of the semiconductor structure before removing the photoresist 13, and a conductive material 14 is also formed in the groove 12a of the aluminum layer 12 to make the imaging clearer. From Figure 3It can be seen that since the side walls of the groove 12a are curved, there are gaps P between the conductive material deposited in the groove 12a and the side walls of the groove 12a. These gaps will cut off the conductive path of aluminum, resulting in hindered current transmission and reduced device reliability.
[0050] Therefore, to solve the above technical problems, an embodiment of the present invention provides a method for manufacturing a semiconductor structure. This method etches an aluminum layer successively with hydrofluoric acid and M2 etchant to form the required pattern, which can reduce the curvature of the groove side walls and the sharp protrusions on the surface of the aluminum layer, and is beneficial to improving the overall performance and long-term stability of the device.
[0051] Figure 4 It is a flowchart of a method for manufacturing a semiconductor structure provided by an embodiment of the present invention. As Figure 4 shown, this manufacturing method includes:
[0052] Step S210: Provide a semiconductor substrate with an aluminum layer on its surface.
[0053] In this embodiment, the semiconductor substrate can be a silicon dioxide or silicon substrate, and the aluminum layer can be deposited on the surface of the semiconductor substrate by physical vapor sputtering.
[0054] Figure 5 It is a schematic diagram of a semiconductor substrate provided in step S210. As Figure 5 shown, this semiconductor substrate 20 includes a substrate 21 and an aluminum layer 22 deposited on the surface of the substrate.
[0055] Step S220: Form a patterned photoresist layer on the aluminum layer, and there are multiple etching windows on the photoresist layer.
[0056] In this embodiment, a photoresist layer can be first coated on the aluminum layer, and then the photoresist layer is exposed and developed using a mask template to remove the part of the photoresist that is not blocked by the mask template, so as to form a patterned photoresist layer. Among them, the positions where the removed part of the photoresist layer is located form multiple etching windows.
[0057] Figure 6 It is a schematic diagram of the semiconductor substrate after performing step S220. As Figure 6 shown, a patterned photoresist layer 23 is formed on the aluminum layer 22 of this semiconductor substrate 20, and etching windows 23a are formed on this photoresist layer.
[0058] Step S230: Use a first etchant to perform a first etching on the aluminum layer through the etching windows to etch and form a first groove on the aluminum layer.
[0059] Among them, the side wall of the first groove is an inclined plane, and the included angle between the side wall of the groove and the surface of the aluminum layer far from the semiconductor substrate is the first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the first groove is less than the thickness of the aluminum layer. The first etching solution contains hydrofluoric acid.
[0060] In this embodiment, step S230 may include:
[0061] Adopt the slot wet etching method, immerse the semiconductor substrate into the first etching tank filled with the first etching solution, and etch the aluminum layer exposed to the etching window to form a first groove on the aluminum layer.
[0062] Among them, slot wet etching is a technique of immersing the wafer or semiconductor material to be etched in a tank filled with a specific etching solution and removing a part of the material on the surface of the wafer or the surface covering film through a chemical reaction. Its principle is to use a chemical reagent to react with the material to be etched to generate a soluble substance or a volatile substance, so as to achieve the removal of the material. In this embodiment, the aluminum layer can be etched once at room temperature (i.e., the current ambient temperature).
[0063] In some implementation manners, before immersing the semiconductor substrate into the first etching tank, pretreatment operations such as rinsing, flushing, and spin-drying can be performed on the semiconductor substrate to ensure the cleanliness of the surface of the semiconductor substrate and the smooth progress of subsequent processes.
[0064] In some implementation manners, the mass fraction of hydrofluoric acid in the first etching solution is 0.10% - 0.25%. Since hydrofluoric acid belongs to a strong acid, reacting with the developed area will etch the aluminum layer, and the effect of high-concentration hydrofluoric acid is particularly obvious. In the solution of the present invention, only hydrofluoric acid etching is required to form a small-angle window with a flat slope surface, providing a more gentle starting etching surface for the second etching to ensure the uniformity and controllability of the second etching. Therefore, in order to reduce the impact on the aluminum layer, low-concentration hydrofluoric acid can be used to improve the adhesion between the photoresist and the aluminum layer, accelerate the etching rate of the aluminum layer, avoid the protrusion of the aluminum layer caused by uneven etching, and prevent over-etching of the aluminum layer.
[0065] Exemplarily, the mass fraction of hydrofluoric acid in the first etching solution is 0.25%, 0.2%, 0.15%, 0.1%, etc., and can be specifically set according to product requirements. The present invention does not limit this.
[0066] In some implementations, the depth of the first groove is less than or equal to 1 / 2 of the thickness of the aluminum layer. That is, the thickness of the aluminum layer etched at one time cannot exceed 1 / 2 of the total thickness of the aluminum layer. Since a large amount of H2 is generated when hydrofluoric acid reacts with Al, the initially generated H2 will adhere to the surface of the aluminum layer, resulting in etching obstruction in some areas, uneven etching of the aluminum layer, and thus rough etching surface. Therefore, in order to ensure the surface roughness of the sidewall of the groove formed by one-time etching, the etching time cannot be too long. By limiting the thickness of the aluminum layer etched at one time, the present invention can ensure the etching effect.
[0067] In some implementations, the thickness of the aluminum layer is 0.5 μ m to 5 μ m. If the thickness of the aluminum layer is too thin, it may lead to insufficient conductivity and cannot meet the application requirements; if the thickness of the aluminum layer is too thick, process steps such as etching may become more complex and time-consuming, increasing the processing difficulty and material cost.
[0068] Figure 7 is a schematic diagram of a semiconductor substrate after performing step S230. As Figure 7 shown, a first groove 22a is formed on the aluminum layer 22 of the semiconductor substrate 20. The sidewall of the first groove 22a is an inclined surface, and the included angle between the sidewall of the first groove 22a and the surface of the aluminum layer 22 away from the semiconductor substrate 21 is a first included angle α1, and the first included angle α1 is an obtuse angle. The distance d between the bottom end (i.e., the end close to the semiconductor substrate 21) of the sidewall of the first groove 22a and the center line of the first groove 22a 11 is less than the distance d between the top end (i.e., the end away from the semiconductor substrate 21) of the sidewall of the first groove 22a and the center line of the first groove 22a 12 .
[0069] In this embodiment, the first included angle α1 is greater than the target included angle α0. The target included angle is the included angle between the sidewall of the through hole formed by directly using the M2 etching solution to etch the aluminum layer in the prior art and the photoresist layer (see Figure 2 α0 in). The target included angle α0 is usually 120° - 130°. At this time, the first groove can be used as a small-angle window with a flat slope surface, providing a more gentle starting etching surface for the second etching to achieve the effect of reducing the generation of convex structures.
[0070] Figure 8 is a FIB imaging schematic diagram of a partial section of a semiconductor structure provided by an embodiment of the present invention. As Figure 8 shown, the sidewall of the first groove 22a is an inclined surface, and there is no obvious convex structure on the surface of the side of the aluminum layer 22 in contact with the photoresist layer 23.
[0071] Step S240: Use a second etching solution to perform secondary etching on the aluminum layer with the first groove through the etching window, so as to etch a second groove on the aluminum layer.
[0072] Among them, the side wall of the second groove is an inclined surface, and the included angle between the side wall of the second groove and the surface of the aluminum layer away from the semiconductor substrate is a second included angle, and the second included angle is smaller than the first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the second groove is greater than or equal to the thickness of the aluminum layer. The second etching solution is an aluminum etchant (also called M2 etchant).
[0073] In this embodiment, step S240 includes:
[0074] Adopt the slot wet etching method, immerse the semiconductor substrate into the second etching tank filled with the second etching solution, and etch the aluminum layer with the first groove exposed to the etching window, so as to form a second groove on the aluminum layer.
[0075] In some implementation manners, before immersing the semiconductor substrate into the second etching tank, pre-treatment operations such as rinsing, flushing and spin-drying can be performed on the semiconductor substrate to ensure the cleanliness of the surface of the semiconductor substrate and the smooth progress of subsequent processes.
[0076] In some implementation manners, the etching temperature in the second etching tank is 30°C to 40°C, and the heating pump in the second etching tank can be adjusted to heat the second etching solution so that the temperature of the second etching solution reaches the etching temperature. Since the aluminum etchant (i.e., M2 etching solution) is sensitive to temperature, setting the etching temperature within this range can ensure the etching rate and etching effect.
[0077] Exemplarily, the etching temperature in the second etching tank is 35°C. Under the condition of 35°C, the etching rate is relatively fast, about
[0078] Exemplarily, the M2 etching solution contains phosphoric acid, nitric acid and acetic acid, and the volume ratio of phosphoric acid, nitric acid and acetic acid is 70:2:12. Among them, nitric acid is used as an oxidant to oxidize Al to generate Al2O3, and then a reaction occurs between phosphoric acid and Al2O3 to generate AlPO4; a small amount of Al directly reacts with phosphoric acid to generate Al(H2PO4)3 and H2. On the one hand, acetic acid is used as a corrosion inhibitor, which can inhibit the ionization of nitric acid, keep the oxidation potential of the solution stable, and maintain the oxidation rate; on the other hand, acetic acid can discharge the small amount of H2 generated by the reaction to prevent the uneven etching or surface roughness phenomenon caused by the attachment of H2 on the Al surface.
[0079] Figure 9 is a schematic diagram of the semiconductor substrate after step S240 is executed, as Figure 9As shown, a second groove 22b is formed on the aluminum layer 22 of the semiconductor substrate 20. The side wall of the second groove 22b is an inclined surface, and the included angle between the side wall of the second groove 22b and the surface of the aluminum layer 22 away from the semiconductor substrate 21 is a second included angle α2, and the second included angle α2 is an obtuse angle. The distance d between the bottom end of the side wall of the second groove 22b and the center line of the second groove 22b 21 is less than the distance d between the top end of the side wall of the second groove 22b and the center line of the second groove 22b 22 .
[0080] In this embodiment, the second included angle α2 is greater than the target included angle α0. For example, the second included angle α2 is greater than 120°.
[0081] Figure 10 is a schematic diagram of FIB imaging of a partial slice of another semiconductor structure provided by an embodiment of the present invention. As Figure 10 shown, the side wall of the second groove 22b is an inclined surface, and there is no obvious convex structure on the surface of the aluminum layer 22 in contact with the photoresist layer 23.
[0082] Step S250: Remove the photoresist layer.
[0083] In this embodiment, the photoresist layer can be removed by a dry or wet method, and the present invention does not limit this.
[0084] In some implementation manners, after performing step S250, the method may further include:[[]]
[0085] Form an insulating layer on the aluminum layer having the second groove.
[0086] In this embodiment, the insulating layer can be a silicon nitride or silicon oxide layer, and can be deposited on the aluminum layer by physical vapor deposition or chemical vapor deposition. Since the surface of the aluminum layer having the second groove etched by the above preparation method has no obvious convexity, it can effectively avoid cracks in the insulating layer deposited on the aluminum layer, meet the high requirements of devices with special functional requirements for the etching angle stability, and significantly improve the overall performance and long-term stability of the devices.
[0087] Based on the same inventive concept, an embodiment of the present invention also provides a semiconductor structure prepared by using the preparation method described in the above embodiment. Figure 11 is a schematic diagram of a semiconductor structure provided by an embodiment of the present invention. As Figure 11As shown, the semiconductor structure 20 includes a semiconductor substrate 21 and an aluminum layer 22 disposed on one side of the semiconductor substrate 21. A second groove 22b is formed on the aluminum layer 22, and the sidewall of the second groove 22b is an inclined surface. The included angle between the sidewall of the second groove 22b and the surface of the aluminum layer 22 away from the semiconductor substrate 21 is a second included angle α2, and the second included angle α2 is greater than the target included angle α0 (see Figure 2 ).
[0088] In this embodiment, the second included angle α2 is greater than 120°. The sidewall of the second groove 22b is substantially a plane, and along the direction perpendicular to the surface of the semiconductor substrate 21, the depth of the second groove 22b is greater than or equal to the thickness of the aluminum layer. The distance d between the bottom end of the sidewall of the second groove 22b and the center line of the second groove 22b 21 is less than the distance d between the top end of the sidewall of the second groove 22b and the center line of the second groove 22b 22 . The distance between the sidewall of the second groove 22b and the center line of the second groove 22b gradually increases in the direction away from the semiconductor substrate 21.
[0089] In some implementation manners, the semiconductor structure 20 further includes an insulating layer disposed on the surface of the aluminum layer 22 away from the semiconductor substrate 21, and the insulating layer can be a silicon nitride or silicon oxide layer.
[0090] It should be noted that the semiconductor structure prepared in the embodiment of the present invention can be used to form devices such as MEMS (Micro-Electro-Mechanical System) sensors.
[0091] The technical solutions provided in the above embodiments of the present application have at least the following technical effects or advantages:
[0092] A semiconductor structure and a preparation method thereof provided by an embodiment of the present invention perform a pretreatment etching by using a first etching solution containing hydrofluoric acid (HF) to form a first groove on the aluminum layer. Among them, hydrofluoric acid can reduce the adhesion between the photoresist and the aluminum layer, promote the acceleration of the aluminum layer etching rate and the improvement of the uniformity, so that the sidewall of the formed first groove is a plane, which is equivalent to pre-forming a small-angle window with a flat slope on the aluminum layer. The formation of this small-angle window provides a more gentle starting etching surface for the secondary etching, thereby ensuring the uniformity and controllability of the secondary etching process, effectively avoiding the generation of convex structures on the surface of the aluminum layer during the subsequent secondary etching using the second etching solution, and making the sidewall of the finally formed second groove present a stable small-angle straight slope morphology, with a flat slope and no protrusions. This precisely controlled etching morphology effectively avoids the problem of cracks in the deposited layer caused by too rapid angle change when depositing other material layers on the aluminum layer, meets the high requirements for the etching angle stability of devices with special functional requirements, and significantly improves the overall performance and long-term stability of the device.
[0093] In the description provided herein, numerous specific details are set forth. It will be understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
[0094] Similarly, it should be understood that in order to streamline this disclosure and help understand one or more of the various inventive aspects, in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all the features of the preceding single embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention.
[0095] It should be noted that the above embodiments illustrate the invention rather than limit the invention, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims.
Claims
1. A method for preparing a semiconductor structure, characterized in that, Including: Providing a semiconductor substrate, on the surface of which there is an aluminum layer; Forming a patterned photoresist layer on the aluminum layer, on which there are a plurality of etching windows; Using a first etching solution, etching the aluminum layer once through the etching windows to etch a first groove on the aluminum layer, the side wall of the first groove being an inclined surface, and the included angle between the side wall of the groove and the surface of the aluminum layer away from the semiconductor substrate being a first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the first groove is less than the thickness of the aluminum layer; the first etching solution contains hydrofluoric acid; Using a second etching solution, etching the aluminum layer with the first groove formed thereon once again through the etching windows to etch a second groove on the aluminum layer, the side wall of the second groove being an inclined surface, the included angle between the side wall of the second groove and the surface of the aluminum layer away from the semiconductor substrate being a second included angle, the second included angle being smaller than the first included angle. Along the direction perpendicular to the surface of the semiconductor substrate, the depth of the second groove is greater than or equal to the thickness of the aluminum layer; the second etching solution is an aluminum etchant; Removing the photoresist layer.
2. The method according to claim 1, wherein The mass fraction of hydrofluoric acid in the first etching solution is 0.10% - 0.25%.
3. The method according to claim 1, characterized in that The step of using a first etching solution to etch the aluminum layer once through the etching windows to etch a first groove on the aluminum layer includes: Adopting a tank wet etching method, dipping the semiconductor substrate into a first etching tank filled with the first etching solution, and etching the aluminum layer exposed to the etching windows to form the first groove on the aluminum layer.
4. The method according to claim 3, characterized in that, The depth of the first groove is less than or equal to 1 / 2 of the thickness of the aluminum layer.
5. The method according to claim 1, characterized in that, The step of using a second etching solution to etch the aluminum layer with the first groove formed thereon once again through the etching windows to etch a second groove on the aluminum layer includes: Adopting a tank wet etching method, dipping the semiconductor substrate into a second etching tank filled with the second etching solution, and etching the aluminum layer with the first groove formed thereon exposed to the etching windows to form the second groove on the aluminum layer.
6. The method according to claim 5, characterized in that, The etching temperature in the second etching tank is 30°C - 40°C.
7. The method according to claim 1, wherein The aluminum etchant contains phosphoric acid, nitric acid and acetic acid, and the volume ratio of the phosphoric acid, the nitric acid and the acetic acid is 70:2:
12.
8. The method according to claim 1, characterized in that, Both the first included angle and the second included angle are obtuse angles, and the second included angle is greater than 120°.
9. The method according to claim 1, characterized in that After removing the photoresist layer, the method further includes: Forming an insulating layer on the aluminum layer with the second groove.
10. A semiconductor structure, characterized in that, Prepared by using the preparation method according to any one of claims 1 - 9, the semiconductor structure includes: A semiconductor substrate; An aluminum layer, provided on one side of the semiconductor substrate, on which a second groove is formed, and the side wall of the second groove is an inclined surface.