Shallow trench isolation structure with rounded corners and method of construction

Abstract

The present application belongs to the technical field of semiconductor manufacturing, and discloses a shallow trench isolation structure with rounded corners and a construction method thereof. The method first constructs a hard mask layer on a substrate, the hard mask layer having an opening, and part of the upper surface of the substrate being exposed from the opening. Then, the substrate exposed outside is subjected to successive cycle etching through a pre-constructed rounded corner model and an etching model, and the width of each etching is gradually decreased. After the successive cycle etching, the construction of the rounded corner is completed. Each cycle etching includes depositing a temporary mask layer on the hard mask layer and part of the exposed substrate, etching the substrate without the deposited temporary mask layer, and then removing the temporary mask layer. Finally, a shallow trench isolation structure is constructed on the substrate adjacent to the constructed rounded corner, and the construction of the shallow trench isolation structure with rounded corners is completed. The method precisely controls the shape and size of the rounded corner, and ensures the smoothness of the rounded corner.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology and relates to a shallow trench isolation structure with rounded corners and its construction method. Background Technology

[0002] Shallow trench isolation (STI) is a widely used isolation element. For example... Figures 1-6 The diagram shown illustrates the step-by-step structure of a method for forming a shallow trench isolation structure. The method includes: as shown... Figure 1 As shown, a hard mask layer 101 is formed on a substrate 100, which may be a Si substrate. The hard mask layer 101 includes an oxide layer 101a (OX layer) and a silicon nitride layer 101b (SiN layer) stacked from bottom to top. A photoresist layer 102 (PR layer) is provided on the surface of the hard mask layer 101. The photoresist layer 102 is exposed and developed to form a patterned photoresist layer; as shown... Figure 2 As shown, using a patterned photoresist layer as a mask, an opening 103 is formed by dry etching of the hard mask layer 101. The opening 103 exposes a portion of the upper surface of the substrate 100, and then the patterned photoresist layer is removed; as... Figure 3 As shown, to complete Figure 2 In the intermediate step device, the hard mask layer 101 serves as a mask, and the substrate 100 is etched using a dry etching process to form multiple shallow trenches 104 in the substrate 100; such as Figure 4 As shown, wet etching and a pull-back process are performed, causing the silicon nitride layer 101b to retract along the direction of the enlarged opening 103; as Figure 5 As shown, wet etching and a pullback process are used to remove the exposed oxide layer 101a from the silicon nitride layer 101b, forming the shoulder 105 of the shallow trench. At the apex of the trench edge in the STI structure, i.e., at the shoulder 105, the gate electric field becomes concentrated, causing inversion at the trench edge and creating a low-threshold path. This leads to increased subthreshold leakage current in the active device, resulting in the Kink effect. In other words, the edge leakage in the STI structure is mainly due to the sharp trench apex causing the gate electric field to concentrate at the corner, leading to a lower threshold at the edge and creating a low-threshold path. Using inclined sidewalls and rounded trench apex corners (generally, the corner radius is approximately 50 nm) can effectively suppress edge leakage current. Figure 6As shown, the shoulder 105 is generally treated by a channel inner wall substrate layer oxidation process (STI liner oxidation) to form a rounded corner 106 in the prior art. However, the rounded corner 106 obtained by the above-mentioned wet etching post-pulling process and channel inner wall substrate layer oxidation process is not smooth enough, and Figures 7-8 It can be seen that the method still has a sharp part at the rounded corner, and the sharper it is, the more likely it is to accumulate electric charge, which cannot fully avoid the problem of low threshold path, affecting the performance of the device. SUMMARY

[0003] In view of the problems in the prior art, the present application provides a shallow trench isolation structure with a rounded corner and a construction method thereof, thereby solving the technical problem that the rounded corner structure constructed at the edge apex of the shallow trench isolation structure in the prior art is not smooth and cannot effectively avoid the low threshold path.

[0004] The present application is realized by the following technical solutions:

[0005] A construction method of a shallow trench isolation structure with a rounded corner, comprising the following steps:

[0006] S1: constructing a hard mask layer on a substrate, the hard mask layer having an opening, and part of the upper surface of the substrate being exposed from the opening;

[0007] S2: performing successive cycle etching on the substrate exposed outside by a pre-constructed rounded corner model and a pre-constructed etching model, and the width of each etching gradually decreasing, and the construction of the rounded corner at the top end of the shallow trench isolation structure being completed after the successive cycle etching; wherein each cycle etching comprises: depositing a temporary mask layer on the hard mask layer and part of the exposed substrate, and etching the substrate without the temporary mask layer, and then removing the temporary mask layer;

[0008] S3: constructing a shallow trench isolation structure on the substrate adjacent to the constructed rounded corner, and completing the construction of the shallow trench isolation structure with a rounded corner.

[0009] Preferably, in the construction process of the rounded corner model, the direction parallel to the substrate is taken as the axis, the direction perpendicular to the substrate is taken as the axis, a two-dimensional coordinate system is established, and a rounded corner model of an arbitrary curve is established in the two-dimensional coordinate system.

[0010] Preferably, the pre-constructed rounded corner model comprises an elliptical structure model, a cosine function model or a one-dimensional quadratic function structure model.

[0011] ​Preferably, the successive cycle etching comprises dividing the intercept of the rounded corner model on the axis into equal parts, and performing successive cycle etching times; or dividing the intercept of the rounded corner model on the axis into equal parts, and performing successive cycle etching times; wherein, the axis is a direction parallel to the substrate, the axis is a direction perpendicular to the substrate.

[0012] Preferably, when the intercept of the rounded corner model on the axis is divided into equal parts, and successive cycle etching is performed, each cycle etching specifically comprises:

[0013] S211: depositing a temporary mask layer on the hard mask layer and the part of the exposed substrate adjacent to the hard mask layer, the dimension of the temporary mask layer on the substrate in the horizontal direction of the substrate is , wherein, is the number of cycles, is the intercept of the rounded corner model on the axis;

[0014] S212: etching the substrate on which the temporary mask layer is not deposited, the etching depth is , wherein, is the difference between the intercept of the rounded corner model on the axis and the axis corresponding to the coordinate point of the rounded corner model with a horizontal distance of ;

[0015] S213: removing the temporary mask layer.

[0016] Preferably, when the intercept of the rounded corner model on the axis is divided into equal parts, and successive cycle etching is performed, each cycle etching specifically comprises:

[0017] S221: depositing a temporary mask layer on the hard mask layer and the part of the exposed substrate adjacent to the hard mask layer, the dimension of the temporary mask layer on the substrate in the horizontal direction of the substrate is , wherein, is the horizontal coordinate corresponding to the coordinate point of the rounded corner model with a vertical distance of from the intercept on the axis, wherein, is the number of cycles, is the intercept of the rounded corner model on the axis;

[0018] S222: etching the substrate without the temporary mask layer, the etching depth being ;

[0019] S223: removing the temporary mask layer.

[0020] Preferably, the intercept of the chamfer model on the axis is divided into equal parts, each part corresponding to a substrate width of 0.2-1 nm; the intercept of the chamfer model on the axis is divided into equal parts, each part corresponding to a substrate thickness of 0.2-1 nm.

[0021] Preferably, the successive cycle etching process is performed by dry etching.

[0022] A shallow trench isolation structure with chamfer, prepared by the method described above, has a chamfer radius of 4-25 nm.

[0023] A semiconductor device comprising a shallow trench isolation structure with chamfer as described above.

[0024] Compared with the prior art, the present application has the following beneficial technical effects:

[0025] The present application discloses a method for constructing a shallow trench isolation structure with chamfer. First, a hard mask layer is constructed on a substrate, the hard mask layer having an opening, part of the upper surface of the substrate being exposed from the opening. Then, a preset chamfer is constructed on the substrate exposed outside by means of successive cycle etching according to a preset chamfer model. In the cycle process, the width of each etching is gradually decreased. Through the successive cycle etching process, a preset chamfer structure can be constructed on the substrate. Before etching, a temporary mask layer is deposited on the hard mask layer and part of the exposed substrate, achieving temporary and effective protection of the hard mask layer and part of the exposed substrate, avoiding damage to the substrate that needs to be retained during the etching process, ensuring that the final chamfer structure is consistent with the preset chamfer structure, and avoiding damage to the hard mask layer during the etching process, ensuring the stability of the final shallow trench isolation structure. The method is simple and convenient to operate. Through the preset chamfer model and etching model, the shape and size of the chamfer can be accurately controlled, ensuring the smoothness of the chamfer.

[0026] Further, in the construction process of the chamfer model, the direction parallel to the substrate is taken as the axis, and the direction perpendicular to the substrate is taken as the axis, a two-dimensional coordinate system is established, and a chamfer model of an arbitrary curve is established in the two-dimensional coordinate system. First, the In a two-dimensional coordinate system, the shape of any curve can be freely defined, thereby constructing a rounded corner model that meets specific requirements. This flexibility makes the method applicable to various complex and diverse application scenarios. Through mathematical formulas or parametric equations, the shape and dimensions of the curve can be precisely described, thus achieving precise control over the rounded corner model. This helps ensure the dimensional accuracy and shape consistency of the final product. Furthermore, in... The rounded corner model established in the two-dimensional coordinate system can be easily imported into simulation software for analysis. Through simulation analysis, the performance of the product, such as stress distribution and deformation, can be predicted, thus providing strong support for optimizing design and process.

[0027] Furthermore, the pre-built rounded corner model includes an elliptical structure model, a cosine function model, or a quadratic function structure model. First, the elliptical structure model, the cosine function model, or the quadratic function structure model all have good curvature, which can effectively ensure the smooth structure of the rounded corner. In addition, these models have standard equations, making them easier to establish and fit.

[0028] Furthermore, the successive cyclic etching includes etching the constructed rounded corner model in... Intercepts on the axis Divide into equal parts and perform successive cyclic etching. Next; or the constructed rounded corner model in Intercepts on the axis Divide into equal parts and perform successive cyclic etching. Next; among them, The axis is a direction parallel to the substrate. The axis is perpendicular to the substrate. First, by using the rounded corner model in... shaft or Dividing the axial intercept equally ensures consistent dimensionality with each etching operation, preventing stress concentration and increased machining difficulty caused by abrupt shape changes. Through successive cyclic etching, the predetermined fillet shape can be gradually approximated, achieving precise construction. This precise control is crucial for ensuring the dimensional accuracy and shape consistency of the product. Furthermore, dividing the fillet model intercept equally results in a relatively small etching amount each time, reducing the impact of a single etching operation on the workpiece, lowering machining difficulty and errors. Successive cyclic etching allows for gradual completion of the fillet shape without the need for complex single-etching operations, thus improving machining efficiency. Moreover, the successive cyclic etching method is suitable for various complex fillet shape designs. By equally dividing the fillet model intercept, flexible etching operations can be performed according to specific requirements. Simultaneously, by precisely controlling the shape and size of each etching operation, the successive cyclic etching method significantly improves machining accuracy, ensuring the smoothness of the fillet surface.

[0029] Further, when the intercept of the rounded corner model on the axis is divided into equal parts, and the successive cycle etching is performed, each cycle etching specifically comprises: S211: depositing a temporary mask layer on the hard mask layer and the partially exposed substrate, the dimension of the temporary mask layer on the substrate along the horizontal direction of the substrate is , wherein, is the number of cycles, is the intercept of the rounded corner model on the axis; S212: etching the substrate without the temporary mask layer, the etching depth is , and the is the difference between the intercept of the rounded corner model on the axis and the corresponding axis when the horizontal coordinate of the rounded corner model is ; S213: removing the temporary mask layer. The intercept of the rounded corner model on the axis is divided into equal parts, and the successive cycle etching is performed, each cycle etching specifically comprises: S221: depositing a temporary mask layer on the hard mask layer and the partially exposed substrate, the dimension of the temporary mask layer on the substrate along the horizontal direction of the substrate is , and the is the horizontal coordinate corresponding to the coordinate point on the rounded corner model with the vertical distance of from the intercept on the axis, wherein, is the number of cycles, is the intercept of the rounded corner model on the axis; S222: etching the substrate without the temporary mask layer, the etching depth is ; S223: removing the temporary mask layer; here, by accurately controlling the dimension of the temporary mask layer deposited on the exposed substrate along the horizontal direction of the substrate and the etching depth, the smoothness of the final obtained rounded corner structure is effectively ensured.

[0030] Further, the intercept of the rounded corner model on the axis is divided into equal parts, and each part corresponds to a substrate width of 0.2-1 nm; the intercept of the rounded corner model on the axis is divided into equal parts, and each part corresponds to a substrate thickness of 0.2-1 nm, first, by dividing the intercept of the rounded corner model on the axis and the The intercept on the axis is finely divided, which can ensure that each etching or deposition operation is performed in a small increment, and this fine division helps to gradually approach and eventually build a smooth rounded corner structure. Since each operation is based on a small increment, the possibility of shape mutation can be significantly reduced, which helps to avoid producing sharp edges or uneven surfaces during the construction process, thereby improving the smoothness of the rounded corner. In addition, since the increment of each operation is small, even if there is a small error, it will not have a significant impact on the finally constructed rounded corner structure, which helps to reduce error accumulation during processing, improve processing accuracy, and by precisely controlling the increment of each operation, the material can be used to the maximum extent, reducing waste, which helps to reduce production costs and improve material utilization.

[0031] Further, the dry etching process is used for the successive cycle etching process, which has a highly anisotropic characteristic, that is, the etching process mainly proceeds in the direction perpendicular to the sample surface, which can accurately control the depth and shape of the etching. In the successive cycle etching process, each etching can be performed in a small increment, thereby gradually approaching and eventually building a smooth rounded corner structure. This precise control helps to avoid shape mutation, reduce error accumulation, and improve processing accuracy. Secondly, in the dry etching process, the etching rate, selectivity and etching profile can be controlled by adjusting parameters such as the type and flow of the gas, the plasma source and the bias power. In the successive cycle etching, these parameters can be optimized for the specific needs of each etching to achieve the best etching effect, which helps to reduce unnecessary damage, protect the hard mask layer and the substrate portion that does not need to be etched, while ensuring the integrity and smoothness of the rounded corner structure. Moreover, dry etching usually has high processing efficiency, which can shorten the processing cycle. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0033] Figure 1 is a cross-sectional view of a shallow trench isolation structure forming method after forming a hard mask layer and a photoresist layer on a substrate;

[0034] Figure 2 is a cross-sectional view of a shallow trench isolation structure forming method after forming a hard mask layer in a substrate;

[0035] Figure 3A cross-sectional view of a shallow trench isolation structure after a shallow trench is formed in a substrate in a method for forming a shallow trench isolation structure;

[0036] Figure 4 A cross-sectional view of a shallow trench isolation structure after an opening of a silicon nitride layer is enlarged in a method for forming a shallow trench isolation structure;

[0037] Figure 5 A cross-sectional view of a shallow trench isolation structure after a shoulder of a shallow trench is formed in a substrate in a method for forming a shallow trench isolation structure;

[0038] Figure 6 A cross-sectional view of a shallow trench isolation structure after a chamfer of a shoulder of a shallow trench is formed in a method for forming a shallow trench isolation structure;

[0039] Figure 7 A TEM slice view of an STI;

[0040] Figure 8 A simulation view of a surface current density and a potential distribution of a chamfer structure obtained in the prior art;

[0041] Figure 9 A view of a chamfer structure being an elliptical structure in one embodiment of the present application;

[0042] Figure 10 A view of an elliptical equation in a two-dimensional coordinate system and a view of a horizontal coordinate intercept being equally divided in one embodiment of the present application; A view of a chamfer model being a cosine function model in one embodiment of the present application;

[0043] Figure 11 A view of a chamfer model being a monomial quadratic function structure model in one embodiment of the present application;

[0044] Figure 12 A cross-sectional view of a substrate after a first etching in one embodiment of the present application;

[0045] Figure 13 A cross-sectional view of a substrate after a second etching in one embodiment of the present application;

[0046] Figure 14 A cross-sectional view of a substrate after a first temporary mask layer is removed in one embodiment of the present application;

[0047] Figure 15 A cross-sectional view of a substrate after a second etching in one embodiment of the present application;

[0048] Figure 16 A cross-sectional view of a substrate after a first temporary mask layer is removed in one embodiment of the present application; ​

[0049] Figure 17 This is a cross-sectional schematic diagram of the smooth rounded corners obtained after cyclic etching in one embodiment of the present invention;

[0050] Figure 18 This is a partial TEM slice image of the shallow trench isolation structure with rounded corners obtained in one embodiment of the present invention;

[0051] Figure 19 This is a simulated diagram of the surface current density and potential distribution of the shallow trench isolation structure with rounded corners obtained in this invention.

[0052] Wherein: 100, substrate; 101, hard mask layer; 101a, oxide layer; 101b, silicon nitride layer; 102, photoresist layer; 103, opening; 104, shallow trench; 105, shoulder; 106, rounded corner; 201, first side shoulder; 202, second side shoulder; 301, first temporary mask layer; 401, smooth rounded corner. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0054] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0055] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0056] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicate the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the present application is usually placed, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0057] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0058] In the description of the embodiments of the present application, it should be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0059] The present application will be described in further detail below with reference to the accompanying drawings:

[0060] Embodiment 1

[0061] The present application provides a construction method of a shallow trench isolation structure with rounded corners, comprising the following steps:

[0062] S1: constructing a hard mask layer on a substrate, the hard mask layer having an opening therein, part of the upper surface of the substrate being exposed from the opening;

[0063] S2: performing successive cycle etching on the substrate exposed outside by means of a pre-constructed rounded corner model and a pre-constructed etching model, and the width of each etching being gradually decreased, and after the successive cycle etching is completed, the construction of the rounded corners at the top of the shallow trench isolation structure is completed; wherein each cycle etching comprises: depositing a temporary mask layer on the hard mask layer and part of the exposed substrate, and etching the substrate without the temporary mask layer, and then removing the temporary mask layer;

[0064] S3: constructing a shallow trench isolation structure on the substrate adjacent to the constructed rounded corner, and completing the construction of the shallow trench isolation structure with rounded corners.

[0065] In the present application, in the process of constructing the chamfered model, the direction parallel to the substrate is taken as the axis, the direction perpendicular to the substrate is taken as the axis, a two-dimensional coordinate system is established, the horizontal direction of the substrate is taken as the axis, and the vertical direction is taken as the axis.

[0066] The core of the above process is step S2, in which, in the process of constructing the chamfered model, a chamfered model of an arbitrary curve is established in a two-dimensional coordinate system.

[0067] More preferably, the pre-constructed chamfered model includes an elliptical structure model, a cosine function model or a one-dimensional quadratic function structure model.

[0068] In a preferred scheme, the successive cycle etching includes dividing the intercept of the chamfered model on the axis into equal parts, and performing successive cycle etching times; or dividing the intercept of the chamfered model on the axis into equal parts, and performing successive cycle etching times.

[0069] In a specific preferred scheme, the intercept of the chamfered model on the axis is divided into equal parts, and each part corresponds to a substrate width, i.e. the size of the horizontal direction of the substrate, which is 0.2-1 nm; the intercept of the chamfered model on the axis is divided into equal parts, and each part corresponds to a substrate thickness, i.e. the size of the vertical direction of the substrate, which is 0.2-1 nm.

[0070] In a more specific preferred scheme, when the intercept of the chamfered model on the axis is divided into equal parts and successive cycle etching is performed, each cycle etching specifically includes:

[0071] S211: depositing a temporary mask layer on the hard mask layer and the part of the exposed substrate adjacent to the hard mask layer, and the size of the temporary mask layer on the substrate in the horizontal direction of the substrate is , wherein is the number of cycles, is the intercept of the chamfered model on the axis;

[0072] S212: etching the substrate without the deposited temporary mask layer, and the etching depth is​​ , the difference between the intercept of the rounded corner model on the axis and the corresponding coordinate on the axis when the rounded corner model is at ;

[0073] S213: removing the temporary mask layer.

[0074] Further, in another more preferred solution, when the intercept of the rounded corner model on the axis is divided into equal parts, and the successive cycle etching is performed, each cycle etching specifically includes:

[0075] S221: depositing a temporary mask layer on the hard mask layer and the portion of the exposed substrate adjacent to the hard mask layer, the dimension of the temporary mask layer on the substrate along the horizontal direction of the substrate is , the is the coordinate on the rounded corner model corresponding to the coordinate point with the perpendicular distance of from the intercept on the axis, wherein, is the number of cycles, is the intercept of the rounded corner model on the axis;

[0076] S222: etching the substrate on which the temporary mask layer is not deposited, the etching depth is ;

[0077] S223: removing the temporary mask layer.

[0078] In the above processing, the substrate can be a silicon substrate. In other embodiments, the substrate can also be a germanium substrate, a silicon-germanium substrate, a silicon carbide substrate, a silicon-on-insulator substrate, or a germanium-on-insulator substrate, etc.

[0079] The hard mask layer can include a silicon oxide layer and a silicon nitride layer stacked in order from bottom to top. The silicon oxide layer and the silicon nitride layer can be formed by a chemical vapor deposition (CVD) process, but are not limited thereto. The silicon oxide layer and the silicon nitride layer can be formed by other methods known in the art. The thickness of the silicon oxide layer and the silicon nitride layer can be set as needed, which is not limited herein.

[0080] The method of forming the opening in the hard mask layer can include: applying a photoresist on the silicon nitride layer to form a photoresist layer; exposing and developing the photoresist layer to form a patterned photoresist layer; etching the silicon nitride layer and the silicon oxide layer with the patterned photoresist layer as a mask to form an opening, the opening exposing part of the upper surface of the substrate; and then removing the patterned photoresist layer. In this embodiment, the number of openings can be multiple. ​

[0081] depositing a temporary mask layer on the hard mask layer and the partially exposed substrate, wherein the temporary mask layer covers the top surface and the side surface of the hard mask layer, and covers the top surface of the partially exposed substrate.

[0082] In one embodiment, the temporary mask layer is an amorphous carbon layer. The amorphous carbon layer can be formed by a physical vapor deposition (PVD) process or a chemical vapor deposition (CVD) process. For example, in the case of forming the amorphous carbon layer by a CVD process, a reaction gas including one or more hydrocarbon gases, such as acetylene (C2H2), propylene (C3H6), or a combination thereof, is introduced into a CVD reaction chamber to form the amorphous carbon layer on the substrate. Of course, the temporary mask layer can also be a polymer layer, which can be formed in a dry etching apparatus. Specifically, the polymer layer is made of a carbon polymer. In the case of forming the polymer layer in the dry etching apparatus, the reaction gas includes fluoromethane (CH3F), difluoromethane (CH2F2), and helium (He), the pressure in the reaction chamber is 3mtorr~8mtorr, and the temperature in the reaction chamber is 80°C~120°C. However, the types of the reaction gas, the pressure in the reaction chamber, and the temperature in the reaction chamber can be adjusted based on the above.

[0083] The above-mentioned cyclic etching process is preferably dry etching. The etching gas includes hydrogen bromide (HBr), chlorine (Cl2), and oxygen (O2), the pressure in the reaction chamber is 5mtorr~10mtorr, and the temperature in the reaction chamber is 80°C~120°C. However, the types of the etching gas, the pressure in the reaction chamber, and the temperature in the reaction chamber in the first etching step can be adjusted based on the above.

[0084] The radius of the rounded corner at the top end of the shallow trench isolation structure prepared by the method of the present application is 4~25nm.

[0085] Example 2

[0086] To further explain the construction of the rounded corner model and the construction of the etching model in the present application, the following examples are provided:

[0087] Suppose the constructed rounded corner structure is an elliptical structure, as shown in Figure 9 , the elliptical equation in the two-dimensional coordinate system and the horizontal intercept is divided into two equal parts. The schematic diagram is shown in Figure 10 , the standard equation of the ellipse is:

[0088]

[0089] wherein, is the intercept of the elliptic curve on the axis; is the intercept of the elliptic curve on the axis; that is is the intercept of the rounded corner model of the elliptic structure on the horizontal axis, is the intercept of the rounded corner model of the elliptic structure on the axis.

[0090] The intercept of the rounded corner model of the elliptic structure on the axis is divided into equal parts, and the elliptic equation can be transformed as:

[0091] ,

[0092] wherein the intercept of the rounded corner model of the elliptic structure on the axis is divided into equal parts, and each part has a spacing of , and the is cycled in turn, and the depth of each etching is , is the number of cycles, and the depth of each etching is:

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] In this process, the size of the temporary mask layer deposited on the exposed substrate in each cycle along the horizontal direction of the substrate is .

[0099] In addition, when the intercept of the rounded corner model on the axis is divided into equal parts, each part has a spacing of , and the is cycled in turn, and the depth of each etching is , and at this time, the elliptic equation can be expressed as:

[0100] ,

[0101] In the process, the size of the temporary mask layer deposited on the exposed substrate each time along the horizontal direction of the substrate is Specifically, the thickness of the temporary mask layer deposited on the exposed substrate each time, i.e., the size of the temporary mask layer on the substrate along the horizontal direction of the substrate is:

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] Embodiment 3

[0108] When the established rounded corner model is a cosine function model, the model structure thereof is shown in Figure 11 Specifically, the model curve equation thereof is:

[0109] ,

[0110] wherein, is the intercept of the rounded corner model on the abscissa, is the intercept of the rounded corner model on the axis.

[0111] When the abscissa intercept is equally divided into portions, the etching depth each time is , is the number of cycles, and specifically the etching depth each time is:

[0112]

[0113]

[0114]

[0115]

[0116]

[0117] When the axis intercept is equally divided into portions, the interval of each portion is , and the etching is performed times in succession, and the etching depth each time is In the process, the thickness of the temporary mask layer deposited on the exposed substrate each time is i.e. the size of the temporary mask layer on the substrate in the horizontal direction of the substrate is Specifically, the thickness of the temporary mask layer deposited on the exposed substrate each time is:

[0118]

[0119]

[0120]

[0121]

[0122]

[0123] Embodiment 4

[0124] When the established rounded corner model is a one-dimensional quadratic function structure model, the model structure is seen in Figure 12 Specifically, the model curve equation is:

[0125] ,

[0126] wherein, is the intercept of the rounded corner model on the horizontal coordinate, is the intercept of the rounded corner model on the axis.

[0127] When the horizontal coordinate intercept is divided into equal parts, the etching depth each time is ,is the number of cycles, and the etching depth each time is specifically:

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] When the intercept of the axis is divided into equal parts, the interval of each part is , and the etching is cycled successively Each etching depth is [number] times. In this process, the thickness of the temporary mask layer deposited on the bare substrate each time is... That is, during each deposition, the dimension (width) of the temporary mask layer located on the substrate along the horizontal direction of the substrate is... Specifically, the thickness of the temporary mask layer deposited on the bare substrate each time is:

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] Example 5

[0140] To further explain the solution of the present invention, the following embodiments are provided:

[0141] like Figure 2 As shown, a hard mask layer 101 is constructed on a substrate, the hard mask layer having an opening 103 through which a portion of the upper surface of the substrate is exposed;

[0142] like Figure 13 As shown, after the first etching, a first shoulder 201 is formed on the substrate. The formation of the first shoulder 201 involves combining the rounded corner model with... Intercepts on the axis The first shoulder 201 is formed by etching after equal segmentation. During the formation of the first shoulder 201, a temporary mask layer is deposited on the hard mask layer 101 and the substrate near the hard mask layer 101. The dimension of the temporary mask layer on the substrate along the horizontal direction of the substrate, i.e., its width, is... Then, the remaining substrate without a deposited temporary mask layer is etched to a depth of [depth missing]. Of course, during the initial etching, a temporary mask layer can be omitted, meaning the deposition can be performed directly at a horizontal distance greater than that of the hard mask layer 101. Etching is performed on the substrate to a depth of [depth missing]. Depositing a temporary mask layer here can significantly improve the structural integrity of the first shoulder 201 and ensure the smoothness of the final rounded corner structure.

[0143] Of course, this step can also be to fillet the corners of the model in... Intercepts on the axis It is obtained by etching based on equal division. In this process, it is possible to first etch at a horizontal distance of less than [missing information] from the hard mask layer 101. A temporary mask layer is constructed on the substrate, and then the substrate without the temporary mask layer is etched to a depth of [depth missing]. Similarly, before the first etching, a temporary mask layer can be skipped, and the deposition can proceed directly at a horizontal distance greater than that of the hard mask layer 101. Etching is performed on the substrate to a depth of [depth missing]. .

[0144] like Figure 14 As shown, during the second cycle of deposition, a first temporary mask layer 301 is deposited on the hard mask layer 101 and the formed first shoulder 201. If this process involves rounded corners and... Intercepts on the axis When the deposition is performed based on equal division, the width of the first temporary mask layer 301 along the horizontal direction of the substrate is... ,Right now Figure 13 In the middle, the horizontal dimension of the first side shoulder 201 formed,

[0145] like Figure 15 As shown, a second etching is performed on the substrate where the first temporary mask layer 301 has not been deposited to form a second shoulder 202. The etching location is at a horizontal distance greater than that from the first temporary mask layer 301. On the substrate, the etching depth is .

[0146] Of course, if the process involves combining the rounded corner model with... Intercepts on the axis Based on equal division, the thickness of the first temporary mask layer 301 deposited is... ,Right now Figure 13 In the process, the horizontal dimension of the first shoulder 201 formed, after the deposition of the first temporary mask layer 301, during the second cycle of etching, the etching position is at a horizontal distance greater than that of the first temporary mask layer 301. On the substrate, the etching depth is .

[0147] like Figure 16 As shown, the structure after removing the first temporary mask layer 301 is fully displayed, showing the first shoulder 201 and the second shoulder 202 formed by two etching processes.

[0148] Combine the rounded corner model with Intercepts on the axis The process of cyclic etching is based on equal division. Next, or the rounded corner model and The intercept on the axis is carried out The process cycle of the cyclic etching is carried out on the basis of the equal division The second time, the final smooth fillet 401 is obtained, and finally, the shallow trench isolation structure is constructed on the substrate adjacent to the obtained fillet, and the construction of the shallow trench isolation structure with the fillet is completed, as shown in Figure 17 .

[0149] Figure 18 The local TEM slice diagram of the finally obtained shallow trench isolation structure with the fillet is shown in the figure, and it can be known from the figure that the fillet structure obtained by the present application is smooth in surface.

[0150] Figure 19 The surface current density and potential distribution simulation diagram of the shallow trench isolation structure with the fillet obtained by the present application are shown in the figure, and it can be known from the figure that the fillet structure obtained by the method is smooth in surface, the high value area (red area and yellow area) of the current density is mainly concentrated in the channel region below “Gox”, and the color transition is relatively flat, without obvious local “peak” or “aggregation” phenomenon, and at the corner of the shallow trench isolation and the substrate, the color smoothly transits from yellow to green, which indicates that the current density is more uniformly distributed when diffusing from the channel to the isolation region, without significant current concentration effect. The potential lines are uniformly distributed as a whole, the potential line interval is wide and parallel in the channel region below “Gox”, which indicates that the potential changes gently with the depth, and at the STI corner, the potential line is curved naturally, without obvious “compression” or “concentration” phenomenon, which indicates that the electric field is uniformly distributed in the region.

[0151] The preferred embodiments of the present application are only used for limiting the present application, and the present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of forming a shallow trench isolation structure with rounded corners, comprising: The method comprises the following steps: S1: constructing a hard mask layer on a substrate, the hard mask layer having an opening, part of the upper surface of the substrate being exposed from the opening; S2: performing successive cycle etching on the substrate exposed outside by a pre-constructed rounding model and a pre-constructed etching model, the width of each etching being gradually decreased, and the construction of the top rounding of the shallow trench isolation structure being completed after the successive cycle etching; wherein each cycle etching comprises: depositing a temporary mask layer on the hard mask layer and part of the exposed substrate, etching the substrate without the temporary mask layer, and then removing the temporary mask layer; S3: constructing a shallow trench isolation structure on the substrate adjacent to the constructed rounding, and completing the construction of the shallow trench isolation structure with the rounding.

2. The method of claim 1 wherein the shallow trench isolation structure is rounded. In the process of constructing the rounded corner model, the direction parallel to the substrate is used as... The axis is defined by a direction perpendicular to the substrate. Axis, Establish Two-dimensional coordinate system, and in the Establish a rounded corner model for any curve in a two-dimensional coordinate system.

3. The method of claim 2, wherein the method further comprises: The pre-constructed rounding model comprises an elliptical structure model, a cosine function model or a one-dimensional quadratic function structure model.

4. The method of claim 2, wherein the method further comprises: The successive cycle etching includes making equal parts of the intercept on the axis of the built rounded corner model and carrying out successive cycle etching times; or making equal parts of the intercept on the axis of the built rounded corner model and carrying out successive cycle etching times.

5. The method of claim 4, wherein the method further comprises: When the rounded corner model is in Intercepts on the axis When etching is performed in equal portions in successive cycles, each etching cycle specifically includes: S211: depositing a temporary mask layer on the hard mask layer and the part of the substrate adjacent to the hard mask layer, the size of the temporary mask layer on the substrate in the horizontal direction of the substrate is wherein, is the number of cycles, is the intercept of the rounded corner model on the axis. S212: Etch the substrate without a deposited temporary mask layer to a depth of [depth missing]. The For rounded corner models The intercept on the axis and the x-coordinate of the fillet model are: Time corresponding The difference between the axes; S213: removing the temporary mask layer.

6. The method of claim 4, wherein the method further comprises: When the rounded corner model is in Intercepts on the axis When etching is performed in equal portions in successive cycles, each etching cycle specifically includes: S221: depositing a temporary mask layer on the hard mask layer and the part of the substrate adjacent to the hard mask layer exposed, the size of the temporary mask layer on the substrate in the horizontal direction of the substrate is , the is the abscissa corresponding to the coordinate point of the vertical distance of the intercept of the rounded corner model on the axis is , wherein is the number of cycles, is the intercept of the rounded corner model on the axis; S222: etching the substrate on which the temporary mask layer is not deposited to a depth of ; S223: removing the temporary mask layer.

7. The method of claim 4, wherein the method further comprises: forming a first photoresist layer on the substrate; and forming a second photoresist layer on the first photoresist layer. The intercept of the rounded corner model on the axis is divided into equal parts, each corresponding to a substrate width of 0.2-1 nm; the intercept of the rounded corner model on the axis is divided into equal parts, each corresponding to a substrate thickness of 0.2-1 nm.

8. The method of claim 1 wherein the shallow trench isolation structure is rounded. The successive cycle etching process is performed by dry etching.

9. A shallow trench isolation structure having rounded corners, characterized in that, The rounding is prepared by the method in any one of claims 1-8, and the radius of the rounding is 4-25 nm.

10. A semiconductor device, characterized by comprising: The method comprises the shallow trench isolation structure with the rounding in claim 9. The method comprises the shallow trench isolation structure with the rounding in claim 9.

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