A method of manufacturing a semiconductor structure

Abstract

This application provides a method for manufacturing a semiconductor structure. The method includes: obtaining a first surface morphology of a structure to be modified, the structure to be modified including a substrate and multiple sidewalls, and the structure to be modified exhibiting parity effects; determining a target incident direction of an ion beam based on the arrangement direction of the multiple sidewalls; determining a target incident angle of the ion beam based on the first surface morphology of the structure to be modified and the sidewall density of the multiple sidewalls; emitting an ion beam at the target incident angle along the target incident direction to etch the structure to be modified using the ion beam, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, reducing the parity effects of the second surface morphology. That is, by selecting a specific incident angle and incident along a specific direction, the physical bombardment force of the ion beam is used to smooth the rounded corners of the sidewall shoulders, achieve squareness of the sidewall etched morphology, improve the high symmetry of the morphology between the sidewalls, and minimize the parity effects.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and in particular to a method for manufacturing a semiconductor structure. Background Technology

[0002] With the development of integrated circuit manufacturing technology, semiconductor process nodes are constantly shrinking, and have now entered the nanometer and atomic scales, undoubtedly posing a huge challenge to photolithography technology. The minimum repeatable period limit for a traditional 193nm photolithography machine is 76nm. When integrated circuit technology advanced to the 14nm FinFET technology node, this traditional exposure process could no longer meet the requirements for pattern definition and formation, necessitating the use of double or multiple patterning techniques. Self-aligned double patterning (SADP) is an advanced photolithography technique used to achieve smaller feature sizes in semiconductor manufacturing.

[0003] refer to Figure 1 As shown, a typical SADP process mainly includes the following steps: (a) Mandrel patterning, which involves forming a mandrel pattern on the substrate surface, which can be accomplished through photolithography and etching. (b) Atomic layer sidewall deposition, which involves depositing a uniform thin film on the surface and sides of the mandrel using atomic layer deposition (ALD) technology to form sidewalls. (c) Sidewall etching and mandrel removal, which involves removing the mandrel using specific chemical methods, leaving the sidewalls. (d) Hard mask etching, where the period of the sidewall pattern left on the substrate surface after mandrel removal is half that of the mandrel pattern, achieving a doubling of spatial pattern density. Plasma etching is used to transfer the sidewall pattern onto a hard mask (HM) in the substrate, thus defining the target pattern.

[0004] However, during the sidewall etching and mandrel removal processes, the ion bombardment effect results in relatively more sidewall loss at the shoulder, leading to excessive shoulder sidewall loss. The actual etched shoulder exhibits rounded corners, and the morphology between adjacent sidewalls is asymmetrical, displaying a typical pitch-walking effect. This pitch-walking effect, caused by pattern loading effect due to differences in the shoulder sidewalls, will transfer to subsequent processes and affect subsequent pattern etching. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a method for manufacturing a semiconductor structure that can reduce the parity effect, produce square sidewalls, and improve the symmetry of the sidewalls.

[0006] This application provides a method for manufacturing a semiconductor structure, the method comprising:

[0007] A first surface morphology of a structure to be modified is obtained. The structure to be modified includes a substrate and a plurality of sidewalls located on one side of the substrate. The first surface morphology of the structure to be modified includes at least the following: the side surface of the sidewall away from the substrate is an inclined surface; the inclined surface and the surface of the substrate are at a fixed angle; the side surface of the sidewall away from the substrate and the sidewall surface of the sidewall form a rounded corner shape; and the inclined directions of the inclined surfaces of adjacent sidewalls are opposite.

[0008] The target incident direction of the ion beam is determined according to the arrangement direction of the multiple sidewalls, and the target incident angle of the ion beam along the target incident direction is determined according to the first surface morphology of the structure to be modified and the sidewall density of the multiple sidewalls.

[0009] An ion beam etching process is used to etch the structure to be modified at a target incident angle along the target incident direction, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the following: the sidewall away from the substrate is a flat surface parallel to the substrate surface; the inclined surface and the substrate surface form a target angle; the sidewall away from the substrate and the sidewall surface form a right angle; and the flat surfaces of adjacent sidewalls are axially symmetrical. The target angle is less than the fixed angle.

[0010] Optionally, the first surface morphology of the structure to be modified includes the undulation difference of the inclined surface; the undulation difference is the difference between the highest point and the lowest point in the inclined surface;

[0011] The step of determining the target incident direction of the ion beam based on the arrangement direction of the plurality of sidewalls, and determining the target incident angle of the ion beam based on the first surface morphology of the structure to be modified and the sidewall density of the plurality of sidewalls, includes:

[0012] The target incident direction of the ion beam is defined as the arrangement direction parallel to the plurality of sidewalls; the target incident angle of the ion beam along the target incident direction is determined based on the difference in undulation of the inclined surface or the sidewall density of the plurality of sidewalls.

[0013] Optionally, determining the target incident angle of the ion beam along the target incident direction based on the first surface morphology of the structure to be modified or the sidewall density of the plurality of sidewalls includes:

[0014] If the sidewall density is greater than the target density or the difference in undulation of the inclined surface is less than or equal to the first difference in undulation, the second target incident angle of the ion beam along the target incident direction is determined according to the first surface morphology of the structure to be modified.

[0015] The step of using an ion beam etching process to emit an ion beam at a target incident angle along the target incident direction to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, includes:

[0016] An ion beam is emitted at a second target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, wherein the undulation difference of the smooth surface included in the second surface morphology is less than the undulation threshold.

[0017] Optionally, determining the target incident direction of the ion beam based on the arrangement direction of the plurality of sidewalls, determining the target incident angle of the ion beam along the target incident direction based on the first surface morphology of the structure to be modified or the sidewall density of the plurality of sidewalls, and using an ion beam etching process to emit an ion beam at the target incident angle along the target incident direction to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, includes:

[0018] If the sidewall density is less than the target density or the difference in undulation of the inclined surface is greater than the first difference in undulation, the first target incident angle of the ion beam is determined according to the first surface morphology of the structure to be modified.

[0019] The target incident direction of the ion beam is the arrangement direction parallel to the plurality of sidewalls; the ion beam is emitted at a first target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a transition surface morphology.

[0020] The second target incident angle of the ion beam along the target incident direction is determined based on the transition surface morphology of the structure to be modified.

[0021] An ion beam is emitted at a second target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the transition surface morphology of the structure to be modified into a second surface morphology.

[0022] Optionally, the incident angle of the first target is smaller than the incident angle of the second target.

[0023] Optionally, the angle range of the first target incident angle is 0°-40°.

[0024] Optionally, the angle range of the second target incident angle is 60°-90°.

[0025] Optionally, the first grid voltage of the ion beam emitted at the first target incident angle is less than the second grid voltage of the ion beam emitted at the second target incident angle.

[0026] Optionally, the voltage range of the first grid voltage of the ion beam incident at the first target incident angle is 50V-800V, and the voltage range of the second grid voltage of the ion beam incident at the second target incident angle is 500V-1500V.

[0027] Optionally, the first fluctuation difference is 15nm, and the fluctuation threshold is 5nm.

[0028] Optionally, a hard mask layer is disposed between the substrate and the sidewall.

[0029] Optionally, the material of the hard mask layer includes a dielectric material or a metal material, wherein the dielectric material is silicon nitride, silicon oxide, or silicon oxynitride, and the metal material is Ta, W, TiN, or TaN; the material of the sidewall is a dielectric material, wherein the dielectric material is silicon nitride, silicon oxide, low-temperature silicon oxide, or silicon oxynitride.

[0030] Optionally, the voltage range of the accelerating grid voltage of the ion beam incident at the first target incident angle is 50-1000V, and the voltage range of the accelerating grid voltage of the ion beam incident at the second target incident angle is 500-1500V.

[0031] Optionally, the range of the grid current for the ion beam incident at the first target incident angle or the second target incident angle is 0.1-1.0A.

[0032] Optionally, the cavity pressure range for the ion beam incident at the first or second target incident angle is 0.01 mT-5 mT, and the total gas flow rate range for the ion beam incident at the first or second target incident angle is 5 sccm-100 sccm.

[0033] Optionally, the etching gas for the ion beam incident at the first target incident angle is one or more of an inert gas, a fluorine-based gas, and a chlorine-based gas, and the etching gas for the ion beam incident at the second target incident angle is an inert gas.

[0034] This application provides a method for manufacturing a semiconductor structure. The method includes: obtaining a first surface morphology of a structure to be modified, wherein the structure to be modified includes a substrate and a plurality of sidewalls located on one side of the substrate; the first surface morphology of the structure to be modified includes at least the following: the sidewalls away from the substrate are inclined surfaces; the inclined surfaces and the surface of the substrate are at a fixed angle; the sidewalls away from the substrate and the sidewall surfaces form rounded corners; and the inclined directions of the inclined surfaces of adjacent sidewalls are opposite, i.e., the structure to be modified has an odd-even effect of rounded corners at the shoulder of the sidewalls; the structure to be modified can be modified using an ion beam etching process; the target incident direction of the ion beam is determined according to the arrangement direction of the plurality of sidewalls; and the ion beam is determined to be incident along the target direction according to the first surface morphology of the structure to be modified and the sidewall density of the plurality of sidewalls. The target incident angle is used to emit an ion beam along the target incident direction to etch the structure to be modified, modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the sidewall away from the substrate being a flat surface parallel to the substrate surface, the inclined surface forming a target angle with the substrate surface, the sidewall away from the substrate forming a right angle with the sidewall surface, and the flat surfaces of adjacent sidewalls being axially symmetrical. The target angle is less than a fixed angle, that is, by selecting a specific incident angle and incident along a specific direction, the physical bombardment force of the ion beam is used to smooth the rounded corners of the sidewall shoulders, achieve squareness of the sidewall etched morphology, improve the high symmetry of the morphology between sidewalls, and minimize the odd-even effect. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A flowchart of a self-aligned dual-patterning process is shown;

[0037] Figure 2(a) shows a schematic diagram of an atomic layer sidewall deposition;

[0038] Figure 2(b) shows a schematic diagram of an ideal sidewall etching process;

[0039] Figure 2(c) shows a schematic diagram of an actual sidewall etching process;

[0040] Figure 3 A schematic diagram of an even / odd effect caused by shoulder rounding is shown;

[0041] Figure 4A schematic flowchart of a semiconductor structure manufacturing method provided in an embodiment of this application is shown;

[0042] Figure 5 This illustration shows a schematic diagram of the first surface morphology of a structure to be etched, provided in an embodiment of this application.

[0043] Figure 6 This illustration shows a schematic diagram of modifying a structure to be etched with a second target incident angle according to an embodiment of this application;

[0044] Figure 7 This illustration shows a schematic diagram of modifying a structure to be etched at a first target incident angle, according to an embodiment of this application.

[0045] Figure 8 This illustration shows a schematic diagram of the second surface morphology of a structure to be etched, provided in an embodiment of this application.

[0046] Figure 9 This illustration shows another schematic diagram of modifying the structure to be etched with a second target incident angle according to an embodiment of this application;

[0047] Figure 10 A schematic flowchart of an ion beam modification process provided in an embodiment of this application is shown;

[0048] Figure 11 A schematic flowchart of an ion beam modification process provided in an embodiment of this application is shown;

[0049] Figure 12 A schematic flowchart of an ion beam modification process provided in an embodiment of this application is shown. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0051] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0052] This application is described in detail with reference to the schematic diagrams. When detailing the embodiments of this application, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of this application. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0053] With the development of integrated circuit manufacturing technology, semiconductor process nodes are constantly shrinking, and have now entered the nanometer and atomic scales, undoubtedly posing a huge challenge to photolithography technology. The minimum repeatable period limit for a traditional 193nm photolithography machine is 76nm. When integrated circuit technology developed to the 14nm FinFET technology node, this traditional exposure process could no longer meet the requirements for pattern definition and formation, necessitating the use of dual or multiple patterning techniques. Currently, the two most common dual patterning techniques in the industry are Self-Aligned Double Patterning (SADP) and Litho-Eich-Litho-Etch (LELE) dual patterning. These techniques utilize dual exposure to define smaller periodic patterns, thereby enabling smaller node process routes.

[0054] Self-aligned double patterning (SADP) is an advanced photolithography technique used to achieve smaller feature sizes in semiconductor manufacturing. It creates dense patterns through two photolithography and etching steps, achieving higher resolution than single-step lithography. In SADP, after the first photolithography creates the pattern, a layer of material is deposited on top, followed by etching to form sidewalls (spacers). These spacer layers act as masks to define the pattern for the second photolithography step. This method allows for feature sizes that are half that of single-step lithography, thereby improving device integration.

[0055] refer to Figure 1As shown, a typical SADP process mainly includes the following steps: (a) Mandrel patterning, which involves forming a mandrel pattern on the substrate surface, which can be accomplished through photolithography and etching. (b) Atomic layer sidewall deposition, which involves depositing a uniform thin film on the surface and sides of the mandrel using atomic layer deposition (ALD) technology to form sidewalls. (c) Sidewall etching and mandrel removal, which involves removing the mandrel using specific chemical methods, leaving the sidewalls. (d) Hard mask etching, where the period of the sidewall pattern left on the substrate surface after mandrel removal is half that of the mandrel pattern, achieving a doubling of spatial pattern density. Plasma etching is used to transfer the sidewall pattern onto a hard mask (HM) in the substrate, thus defining the target pattern.

[0056] Self-aligned dual patterning (SADP) technology is considered one of the most promising technologies in the current semiconductor process, especially for manufacturing devices smaller than 22nm. It enables precise control of the critical dimension (CD) of the pattern, reduces the stringent requirements for secondary mask overlap, and minimizes line edge roughness (LER). These advantages make SADP technology extremely attractive for integrated circuit manufacturing, especially for NAND memory and logic devices, playing a crucial role in both memory and logic device processes. It is particularly important in NAND memory manufacturing, where its unique process steps and advantages make it stand out in high-precision patterning. The structural characteristics of NAND memory dictate its high precision requirements for patterning; the dense line spacing makes critical dimension control especially critical. Through multiple patterning techniques, such as quadruple patterning, we can achieve even smaller feature sizes. Similarly, in logic devices, when the technology advanced to the 14nm FinFET technology node, the fin width was 10nm, smaller than the smallest size that immersion lithography could manufacture. Therefore, the active region of FinFET devices is not formed by ordinary photolithography, but by SADP technology. The development of SADP technology has promoted the miniaturization of devices.

[0057] SADP technology can also be used to develop Self-Aligned Quadruple Patterning (SAQP) or Self-Aligned Multiple Patterning (SAMP) technologies to achieve smaller critical dimensions and more refined pattern definitions. SAXP technology reduces the requirements for lithography machines and eliminates the overlay problem, greatly promoting the miniaturization of integrated circuit technology and playing a crucial role in integrated circuits.

[0058] SADP technology is not without its costs. Compared to other dual patterning techniques, it requires more process steps, such as sidewall ALD deposition and sidewall etching. This not only makes SADP relatively expensive, but the additional process steps also mean more challenges in process precision control. The main difficulty lies in controlling the even / odd effect during etching, primarily in the precision control of critical sidewall dimensions and etching morphology, all of which are directly related to the performance of the final device. Specifically, this includes:

[0059] 1. Sidewall Critical Dimension Control: SADP technology requires precise control of sidewall critical dimensions to ensure the accuracy of the drawing. Any deviation in CD (Critical Dimension) can lead to distortion or failure of the final drawing.

[0060] 2. Etching morphology control: Controlling the etching morphology is also a major challenge. It is necessary to ensure the uniformity and consistency of the etching process and avoid the surface roughness (loading) effect introduced by the difference in etching morphology, which can cause performance differences between different devices.

[0061] 3. Multiple exposures reduce yield: Using SADP technology for multiple exposures will significantly reduce yield because each exposure and etching may introduce new errors and variations, increasing the risk of failure and thus increasing process costs.

[0062] The asymmetric etching behavior during SADP process is collectively referred to as the Pitch Walking effect. This effect can cause distortion of the final pattern and uneven stress in the lines, and in severe cases, it can lead to line collapse, ultimately affecting the stable performance of the device. Reducing the Pitch Walking effect has become a challenge for the SADP process.

[0063] In actual etching processes, especially sidewall etching and mandrel removal, severe parity effects are introduced, significantly impacting subsequent processes and the final device performance. The sidewall behavior after mandrel removal is a critical step in self-aligned dual-patterning processes; its feature size, sidewall morphology, line roughness, and substrate recess all have a significant impact on subsequent processes.

[0064] In current self-aligned multi-patterning techniques, such as SADP, the ideal outcome after sidewall etching is to leave a relatively square top, as shown in Figure 2(b), to ensure uniform stress on the sidewall lines and eliminate the parity effect. However, in actual processes, isotropic atomic layer sidewall deposition and sidewall etching inevitably result in rounded shoulders on the sidewalls. This means that the morphology of the shoulder etching between adjacent sidewalls exhibits asymmetry, significantly contributing to the parity effect. Rounded shoulders are formed during isotropic atomic layer sidewall deposition, as shown in Figure 2(a). Similarly, during sidewall etching, due to the ion bombardment effect, the sidewall loss at the shoulders is relatively high, resulting in excessive shoulder sidewall loss, as shown in Figure 2(c). The actual sidewall etching shoulders are rounded, and the morphology between adjacent sidewalls is asymmetrical, exhibiting a typical parity effect.

[0065] Figure 2(c) shows four sidewalls, 1, 2, 3, and 4. The opening effect between sidewalls 1-2 and 2-3 differs significantly. During plasma etching, charged particles / active groups can more easily enter from the region between sidewalls 2-3, and similarly, etching byproducts can more easily escape from this region. This results in region 2-3 having a higher etching effect than region 1-2. Figure 3 As shown, the parity effect caused by pattern loading effect due to differences in the shoulder sidewalls will transfer to subsequent processes, triggering parity effects in subsequent hard mask etching and pattern definition stages. For example, there may be differences in feature dimensions between patterns (CD1 < CD2), and the overall morphology may exhibit a taper due to stress accumulation. In addition, for relatively high sidewalls, when the non-uniform stress caused by this parity effect accumulates to a certain extent, it may even cause line collapse, resulting in defects and producing greater process defects. The accumulation and transmission of parity effects caused by these asymmetries ultimately leads to distortion of the target pattern, greatly reducing pattern accuracy and ultimately inhibiting the stable expression of device electrical properties. Especially in SADP applications below the 22nm node, the requirements for pattern accuracy are more stringent. Deviations in critical dimensions and etching morphology will seriously affect the electrical performance of the device, such as the definition of channel width and poor electron and hole characteristics of NMOS / PMOS matching.

[0066] Eliminating the rounded corner morphology of the sidewall shoulders and controlling the highly symmetrical square sidewall morphology has a significant effect on reducing the odd-even effect in double patterning processes. In particular, when the size is further reduced, the square sidewall will also have a key impact on the self-aligned quadruple patterning (SAQP) process applied to smaller critical size processes.

[0067] Based on this, this application provides a method for manufacturing a semiconductor structure. The method includes: obtaining a first surface morphology of a structure to be modified, wherein the structure to be modified includes a substrate and a plurality of sidewalls located on one side of the substrate; the first surface morphology of the structure to be modified includes at least the following: the sidewall away from the substrate is an inclined surface; the inclined surface and the surface of the substrate form a fixed angle; the sidewall away from the substrate and the sidewall surface of the sidewall form a rounded corner shape; and the inclined directions of the inclined surfaces of adjacent sidewalls are opposite, i.e., the structure to be modified has an odd-even effect of rounded corners at the shoulder of the sidewall; the structure to be modified can be modified using an ion beam etching process; the target incident direction of the ion beam is determined according to the arrangement direction of the plurality of sidewalls; and the direction of the ion beam along the target is determined according to the first surface morphology of the structure to be modified and the sidewall density of the plurality of sidewalls. The target incident angle of the incident direction is used to emit an ion beam along the target incident angle to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the following: the sidewall away from the substrate is a flat surface parallel to the substrate surface; the inclined surface is at a target angle to the substrate surface; the sidewall away from the substrate and the sidewall surface of the sidewall form a right angle; and the flat surfaces of adjacent sidewalls are axially symmetrical. The target angle is less than a fixed angle. That is, by selecting a specific incident angle and incident along a specific direction, the physical bombardment force of the ion beam is used to smooth the rounded corners of the sidewall shoulders, achieve the squareness of the sidewall etched morphology, improve the high symmetry of the morphology between sidewalls, and minimize the odd-even effect.

[0068] To better understand the technical solution and effects of this application, the specific embodiments will be described in detail below with reference to the accompanying drawings.

[0069] See Figure 4 The figure is a schematic flowchart of a semiconductor structure manufacturing method provided in an embodiment of this application.

[0070] The semiconductor structure manufacturing method provided in this embodiment includes the following steps:

[0071] S101, Obtain the first surface morphology of the structure to be modified. The structure to be modified includes a substrate and a plurality of sidewalls located on one side of the substrate. The first surface morphology of the structure to be modified includes at least the side surface of the sidewall away from the substrate being an inclined surface, the inclined surface and the surface of the substrate forming a fixed angle, the side surface of the sidewall away from the substrate and the sidewall surface of the sidewall forming a rounded corner shape, and the inclined directions of the inclined surfaces of adjacent sidewalls being opposite.

[0072] In embodiments of this application, the structure to be modified includes a substrate 110 and a plurality of sidewalls 120 located on one side of the substrate 110. The substrate 110 can be a semiconductor substrate, such as a silicon substrate (Si substrate). The sidewalls 120 are columnar structures located on one side of the substrate 110 after undergoing sidewall etching and core removal processes. The plurality of sidewalls 120 have a fixed sidewall density. The sidewalls are made of dielectric materials, such as silicon nitride (Si3N4), silicon oxide (SiO2), low-temperature silicon oxide (LTO), or silicon oxynitride (SiON).

[0073] After the sidewall etching and mandrel removal processes, the structure to be modified has a first surface morphology. This first surface morphology includes at least the following: the side surface of the sidewall 120 away from the substrate 110 is an inclined surface; the inclined surface and the surface of the substrate 110 form a fixed angle; the side surface of the sidewall 120 away from the substrate 110 and the sidewall surface of the sidewall 120 form a rounded corner shape; and the inclined directions of adjacent sidewall 120 inclined surfaces are opposite. (Reference) Figure 5 As shown, the shoulder of the sidewall 120 exhibits a rounded etched morphology, and the rounded corners of adjacent sidewalls 120 face opposite directions, showing a clear asymmetry.

[0074] S102, determine the target incident direction of the ion beam based on the arrangement direction of the multiple sidewalls, and determine the target incident angle of the ion beam along the target incident direction based on the first surface morphology of the structure to be modified and the sidewall density of the multiple sidewalls.

[0075] Ion beam etching is an atomic-level high-precision surface processing technology. It utilizes a neutral ion beam with specific energy to bombard the wafer surface. By adjusting parameters such as the ion beam's energy, incident angle, and gas composition, the trajectory of the colliding particles can be controlled. Combined with interaction mechanisms such as sputtering, scattering, and chemical reactions, it achieves precise planar modification at the atomic level. The most significant advantage of ion beam etching is its ability to provide directional etching with an angle, where the etching direction is related to the incident angle. This allows for high process flexibility and provides sophisticated pattern modification solutions in specific scenarios.

[0076] In the embodiments of this application, ion beam etching technology can be used to etch the structure to be modified to reduce the parity effect. Considering that the structure to be modified is a three-dimensional structure, when etching the structure to be modified with an ion beam, it is necessary to determine the incident direction of the ion beam and the incident angle along the incident direction. The incident angle is defined as the angle between the incident direction of the ion beam and the normal of the inclined surface. The target incident direction of the ion beam can be determined according to the arrangement direction of the multiple sidewalls, and the target incident angle of the ion beam along the target incident direction can be determined according to the first surface morphology of the structure to be modified and the sidewall density of the multiple sidewalls 120. That is, the ion beam etches the structure to be modified along a specific direction and at a specific angle.

[0077] Specifically, the target incident direction of the ion beam can be set parallel to the arrangement direction of the multiple sidewalls 120, and the arrangement direction of the multiple sidewalls 120 is perpendicular to the extension direction of the sidewalls 120. That is, the target incident direction of the ion beam is along the arrangement direction of the multiple sidewalls 120 and perpendicular to the extension direction of the sidewalls 120. Considering the shielding effect and directionality of the ion beam, the incident direction of the ion beam is usually parallel to the extension direction of the sidewalls 120 to maximize the bombardment effect of the ion beam on the first surface morphology. At the same time, incidenting the ion beam along the target incident direction and at the target incident angle can avoid damage to the sidewalls of the sidewalls 120 and the bottom film of the sidewalls 120, and minimize the new parity effect introduced by the ion beam process itself.

[0078] refer to Figure 6 As shown, Figure 6 A cross-sectional schematic diagram of a structure to be modified is shown, which is obtained by taking a section along the arrangement direction of the sidewalls 120. Figure 6 In the middle, the target incident direction is the arrangement direction of the sidewall 120, so the plane containing the target incident direction is parallel to the plane of the section.

[0079] For the same material, the etching rate varies under different ion beam incident angles. Taking inert gases as an example, the overall etching rate is nearly parabolic, with the highest etching rate occurring near the mid-angle and the lowest at high angles; that is, the etching rate of undulating surfaces is greater than that of flat surfaces. Based on this characteristic, and by selecting a specific ion beam incident angle, the etching rate difference caused by the difference in the equivalent incident angle of the etched surface can be used to modify the pattern of a specific etched morphology, such as smoothing out local undulations. Therefore, the first surface morphology of the structure to be modified also includes the difference in the undulation of the inclined surfaces of the sidewalls 120, where the undulation difference is the difference between the highest and lowest points on the inclined surfaces. The target incident angle of the ion beam is determined based on the undulation difference of the inclined surfaces or the sidewall density of multiple sidewalls 120.

[0080] As one possible implementation, if the sidewall density is greater than the target density or the difference in surface roughness of the inclined surface is less than or equal to the first difference in surface roughness, the second target incident angle of the ion beam is determined based on the first surface morphology of the structure to be modified. For example, if the first difference in surface roughness is 15 nm, the second target incident angle is an angle with a larger incident angle, as referenced. Figure 6 As shown. Preferably, the first fluctuation difference is 10 nm.

[0081] As another possible implementation, if the sidewall density is less than the target density or the difference in surface roughness of the inclined surface is greater than the first difference in surface roughness, the first target incident angle of the ion beam is determined based on the first surface morphology of the structure to be modified. For example, the first target incident angle is an angle with a smaller incident angle, as referenced. Figure 7 As shown.

[0082] In other words, the ion beam incident angle for etching the structure to be modified can be determined by the difference in sidewall density or the undulation of the inclined surface. This can be mainly divided into two categories, using different ion beam incident angles to maximize the reduction of the parity effect of the structure to be modified.

[0083] S103, using an ion beam etching process, an ion beam is emitted at a target incident angle along the target incident direction to etch the structure to be modified, modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the sidewall away from the substrate being a flat surface parallel to the substrate surface, the inclined surface and the substrate surface forming a target angle, the sidewall away from the substrate and the sidewall surface forming a right angle, and the flat surfaces of adjacent sidewalls being axially symmetrical; the target angle is less than a fixed angle.

[0084] In the embodiments of this application, after determining the target incident direction of the ion beam and the target incident angle along the target incident direction, an ion beam etching process can be used to emit an ion beam at the target incident angle along the target incident direction to etch the structure to be modified, modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the following: the side surface of the sidewall 120 away from the substrate 110 is a flat surface parallel to the surface of the substrate 110; the inclined surface and the surface of the substrate 110 form a target angle; the side surface of the sidewall 120 away from the substrate 110 and the sidewall surface of the sidewall 120 form a right angle shape; and the flat surfaces of adjacent sidewalls 120 are axially symmetrical. The target angle is less than a fixed angle, that is, the inclination of the inclined surface is reduced. Figure 8As shown. In other words, by using ion beam etching, the first surface morphology, which has rounded shoulders, asymmetry between adjacent sidewalls, and odd-even effects, is modified into a second surface morphology with square shoulders, symmetrical height between adjacent sidewalls, and no odd-even effects. That is, the rounded shoulders are completely removed, the sidewalls have a near-standard square shape, and the overall undulation of the top is reduced.

[0085] Modifying the first surface morphology into a second surface morphology can be achieved through various etching processes depending on the specific characteristics of the first surface morphology.

[0086] As a possible implementation, when the sidewall density is greater than the target density or the difference in surface roughness of the inclined surface is less than the first difference in surface roughness, a larger incident angle can be used to avoid damage to the bottom of the sidewall 120 and the substrate 110, and to refine the inclined surface. That is, a larger second target incident angle is used. The angle range of the second target incident angle is 60°-90°. An ion beam etching process is used to emit an ion beam at the second target incident angle along the target incident direction to etch the structure to be modified, modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes a smooth surface with a roughness difference less than a roughness threshold, where the roughness threshold is 5 nm. Figure 6 and Figure 8 As shown. Preferably, the fluctuation threshold is 3nm.

[0087] As another possible implementation, considering that if the unevenness difference of the inclined surfaces included in the first surface morphology of the structure to be modified is large, at least one ion beam etching process may be required, for example, two ion beam etching processes. The ion beam incident angle of each ion beam etching process is determined according to the surface morphology of the structure to be modified. If the sidewall density is less than the target density or the unevenness difference of the inclined surfaces is greater than the first unevenness difference, a smaller incident angle can be used to significantly smooth the inclined surfaces, i.e., the first target incident angle is smaller. The angle range of the first target incident angle is 0°-40°. The ion beam etching process is used to etch the structure to be modified by emitting an ion beam at the first target incident angle along the target incident direction, as described in the reference. Figure 7 As shown, the first surface morphology of the structure to be modified is modified into a transitional surface morphology. The difference in undulation of the sidewall surfaces included in the transitional surface morphology is smaller than the difference in undulation of the first surface morphology, and the orientation of the rounded corners of the sidewalls is also basically the same. The second target incident angle of the ion beam is determined according to the transitional surface morphology of the structure to be modified. An ion beam is emitted at the second target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified. (Refer to...) Figure 9 As shown, the transition surface morphology of the structure to be modified is modified into a second surface morphology, as referenced. Figure 8As shown in the diagram, the incident angle of the first target is greater than that of the second target. That is, by incidenting the ion beam at the first target angle, the etching rate difference between the different undulations of the ion beam is utilized to optimize the undulation amplitude of the rounded corners at the top of the sidewall, achieving rough finishing of the rounded corners and obtaining a transitional surface morphology. Then, by incidenting the ion beam at the second target angle, the collimation of the ion beam is used to smooth the rounded corners at the top of the sidewall, achieving fine finishing of the rounded corner undulations and obtaining a second surface morphology.

[0088] In the embodiments of this application, when ion beam etching is performed on the structure to be modified, in addition to irradiating the ion beam at the target incident angle along the target incident direction, parameters such as the ion beam incident grid voltage, grid current, accelerating grid voltage, cavity pressure range, etching gas, and total gas flow rate are also set.

[0089] As one possible implementation, the first grid voltage for emitting an ion beam at a first target incident angle is less than the second grid voltage for emitting an ion beam at a second target incident angle. Since the second target incident angle is greater than the first target incident angle, the ion beam at the second target incident angle exhibits a lower etching rate. Therefore, to improve the etching effect, the grid voltage of the ion beam at the second target incident angle can be increased to increase the energy of the ion beam and improve the etching rate.

[0090] The following section describes the specific process of etching the structure to be modified, taking the modification of the first surface morphology into the second surface morphology through two ion beam etching processes as an example.

[0091] An ion beam is incident at a first target incident angle along the target incident direction to modify the first surface morphology, initially reducing the undulation of the sidewall top rounded corners and achieving coarse finishing of the sidewall rounded corners. This results in a transitional surface morphology, namely, near-flattened sidewall shoulders with an overall top undulation ≤10nm and near-symmetrical behavior between adjacent sidewalls. The first target incident angle ranges from 0° to 40°, depending on the initial morphology of the sidewall shoulder rounded corners. Typically, a relatively low angle is chosen to maximize the equivalent etching rate difference between different undulation regions of the rounded corner, thereby significantly optimizing the rounded corner undulations. The first gate voltage (BMV) of the ion beam incident at the first target incident angle ranges from 50V to 800V. Based on the differences in sidewall material properties (dielectric / metallic materials), different energies are selected to maximize the efficiency of sputtering etching products at the sidewall rounded corners while ensuring controllable overall sidewall height loss. Combined with the control of etching rate differences between different undulation regions, a significant improvement in the rounding of the sidewall shoulders is achieved. The accelerating grid voltage (ACV) of the ion beam incident at the first target incident angle ranges from 50 to 1000 V. ACV affects the global distribution of the ion beam. Adjusting the ACV allows for adjustment of the ion beam density distribution across the core-middle-edge region of the structure to be modified, achieving uniformity across different regions and resulting in high wafer-level uniformity. The specific ACV can be set based on the overall mapping uniformity of the sample. The screen current (BMI) of the ion beam incident at the first target incident angle ranges from 0.1 to 1.0 A, depending on the sidewall material type and the rounded corners of the sidewall shoulders. BMI affects the ion beam density; a lower BMI results in a lower etching rate, which is beneficial for enhancing control over the loss at the sidewall shoulders and for collaboratively adjusting the differences in etching rates at different undulations. The cavity pressure range for the ion beam incident at the first target incident angle is 0.01 mT-5 mT, and the total gas flow rate ranges from 5 sccm-100 sccm. The etching gas is one or more of inert gases, fluorine-based gases, and chlorine-based gases. The inert gases include one or more of He, Ne, Ar, Kr, and Xe, and the fluorine-based gases include C. x F y Where x and y are positive integers, C x F y The etching gases include one or more of NF3, SF6, WF6, CHF3, CH2F2, and CH3F, while chlorine-based gases include one or more of Cl2, BCl3, CCl4, and SiCl4. The specific etching gas chosen depends on the material of the sidewalls.

[0092] The transition surface morphology is modified by ion beam incident at a second target incident angle along the target incident direction. The collimation of the ion beam is used to smooth the top rounded corners of the sidewalls, achieving fine finishing of the sidewall rounded corner undulations and obtaining the second surface morphology. The first grid voltage of the ion beam incident at the first target incident angle is less than the second grid voltage of the ion beam incident at the second target incident angle, and the first target incident angle is less than the second target incident angle. The second surface morphology is characterized by complete removal of the rounded corners of the sidewall shoulders, a near-standard square shape of the sidewalls, an overall top undulation ≤3nm, and high symmetry between adjacent sidewalls with no parity effect. The angle range of the second target incident angle is 60°-90°, determined by the overall undulation of the sidewall rounded corners after etching the structure to be modified using the first target incident angle. For low-undulation surfaces, an angle range of 60-90° is typically chosen. Utilizing the strong directionality of the ion beam, the low divergence of the ion beam is controlled to achieve higher recognition of the undulating surface, ultimately achieving fine smoothing. The voltage range of the second grid voltage for the ion beam incident at the second target incident angle is 500V-1500V, depending on the differences in the characteristics of the pre-removed material (dielectric / metallic material) and the undulations. A high-energy process is selected to increase the initial kinetic energy of the ion beam, thereby increasing its collimation. Strong directional collimation is used to achieve precise identification and directional elimination of undulations. The voltage range of the accelerating grid voltage for the ion beam incident at the second target incident angle is 500-1500V. The ACV (Accelerated Convection Voltage) affects the beam divergence angle and collimation of the ion beam; a higher ACV helps improve the collimation and achieve more precise directional smoothing of surface undulations. The grid current for the ion beam incident at the second target incident angle ranges from 0.1-1.0A, depending on the sidewall material type and the transition surface morphology. The BMI (Browser Mass Index) affects the ion beam density; a lower BMI achieves a lower ion density, reduces collisions between ion beams, enhances beam collimation, and facilitates precise modification of the rounded corner undulations on the sidewall shoulder. The cavity pressure range for the ion beam incident at the second target incident angle is 0.01 mT-5 mT, and the total gas flow rate ranges from 5 sccm-100 sccm. The low cavity pressure helps increase the mean free path of molecules, thereby reducing the probability of collisions between ions, improving the collimation of the ion beam, and facilitating precise modification of the target area. The etching gas used for the ion beam incident at the second target incident angle is an inert gas, including one or more of He, Ne, Ar, Kr, and Xe. Inert gases have higher ion quality and are easier to control the directionality of the ion beam.

[0093] In other words, based on the first and second target incident angles along the target incident direction, the ion beams are used to perform two surface modifications to completely remove the rounded corner morphology of the sidewall shoulder. The sidewall has a near-standard square morphology, the overall top undulation is ≤3nm, and the adjacent sidewalls exhibit high symmetry.

[0094] In embodiments of this application, a hard mask layer may be disposed between the substrate and the sidewalls. The hard mask layer can be etched using the sidewalls as a mask to transfer the pattern to the hard mask layer. Subsequently, the substrate can be etched using the hard mask layer as a mask to pattern the substrate. There is an etching selectivity between the sidewalls and the hard mask layer. The material of the hard mask layer includes a dielectric material or a metallic material. The dielectric material is, for example, silicon nitride (Si3N4), silicon oxide (SiO2), or silicon oxynitride (SiON), and the metallic material is, for example, Ta, W, TiN, or TaN.

[0095] This application can achieve high-fidelity pattern transmission without additional hard mask layers, saving hard mask layers and freeing up the flexibility of sidewall material selection. It is not limited by the etching selection ratio between multiple film layers and multiple processes, and at the same time, it can effectively eliminate the odd-even effect.

[0096] In practical applications, this application addresses the parity effect caused by asymmetric etching topography in self-aligned multi-patterning technology. Self-aligned multi-patterning technology includes self-aligned dual-patterning, self-aligned quadruple-patterning, and self-aligned multi-patterning. The ion beam etching process in this application is a single-chamber in-situ process, avoiding process complexity, improving device electrical stability, and effectively reducing process costs, transmission time, and throughput. This application provides a cross-wafer-level, in-situ global surface modification solution, minimizing parity effects, achieving high-fidelity transfer of defined patterns, avoiding pattern distortion and potential line collapse, and ultimately improving device electrical performance. This application is applicable to advanced process technology fields such as logic devices (logic, Fin-FET, etc.) and memory devices (DRAM, Nor Flash NAND, 3D NAND, etc.).

[0097] Therefore, this application addresses the parity effect caused by asymmetric rounded corner etching morphology of the sidewall shoulders during the self-collimation multi-patterning process. Based on ion beam lithography (IBS) or reactive ion beam lithography (RIBS), it provides a cross-wafer-level, in-situ, global sidewall shoulder etching morphology repair scheme to reduce the parity effect and improve the stable expression of device performance. Specifically, by selecting specific energy and incident angle, and incident along a specific direction, the physical bombardment force of the ion beam and the control of sputtering byproducts are used to achieve the smoothing of the rounded corners of the sidewall shoulders, realize the squareness of the sidewall etching morphology, improve the high symmetry of the morphology between sidewalls, reduce the differences between critical dimensions, minimize the parity effect, achieve high-fidelity transfer of the defined pattern, avoid pattern distortion and potential line collapse, and ultimately improve the expression of the device's electrical performance.

[0098] The following three examples will be used to illustrate the method of this application in detail.

[0099] The first example illustrates the parity effect caused by asymmetric sidewall shoulder rounded corner topography in the SADP process of FinFET manufacturing, a logic device. The specific process flow for surface modification of the FinFET using ion beam shaping is provided below. Figure 10 As shown.

[0100] In the field of logic device manufacturing, after the mandrel removal step in the SADP process, the asymmetric appearance of the rounding morphology at the sidewall shoulders, coupled with the selectivity ratio between the mandrel / sidewall / hard mask layers, leads to distortion of the subsequent sidewall morphology. This, in turn, causes a parity effect, resulting in distortion of the subsequent etching morphology and electrical failure of the device. In SADP self-aligned dual imaging technology, this parity effect manifests as rounded corner morphology at the sidewall shoulders, with a rounding undulation height ≥15nm, and the rounded corners of adjacent sidewalls facing opposite directions, exhibiting a typical parity effect. The overall wafer uniformity is also observed, with the sidewall height in the Edge region being higher than that in the Center and Middle regions. The structure to be modified, from bottom to top, consists of the substrate, the hard mask layer, and the sidewalls. The mandrel material is amorphous carbon (a-SOC), the sidewall material is silicon nitride (Si3N4), and the hard mask layer material is silicon oxide (SiO2). The first surface morphology is modified by an ion beam incident at the first target incident angle, initially reducing the undulation amplitude of the sidewall top rounded corners, achieving coarse finishing of the sidewall rounded corners, and obtaining a transitional surface morphology, namely, near-flattening of the sidewall shoulder, with an overall top undulation ≤8nm, and near-symmetrical behavior between adjacent sidewalls. The first target incident angle is 20°, a relatively low angle, to maximize the equivalent etching rate difference between different undulation regions of the rounded corner, thereby significantly optimizing the rounded corner undulation. The screen voltage of the ion beam incident at the first target incident angle is 200V. Based on the sidewall material Si3N4, choosing 200V energy ensures that the overall height loss of the sidewall is controllable while maximizing the efficiency of sputtering etching products at the sidewall rounded corners. Combined with the control of the etching rate difference between different undulation regions, a significant improvement in the rounding of the sidewall shoulder is achieved. The accelerating grid voltage of the ion beam incident at the first target incident angle is 300V. A low ACV allows for ion beam divergence towards the edge region, achieving an ion beam density in the edge region greater than that in the center and middle regions. This results in higher etching rates and optimizes the uniformity of the edge region's overall height compared to the center and middle regions, achieving high uniformity across the entire wafer level. The screen current for the ion beam incident at the first target incident angle is set to 0.5A, determined based on the sidewall material being Si3N4 and the initial shoulder radius undulation being ≥15nm. BMI affects the ion beam density; a low BMI results in a low etching rate, which is beneficial for enhancing control over the sidewall shoulder loss and coordinating the adjustment of etching rate differences at different undulations. The cavity pressure for the ion beam incident at the first target incident angle is 1mT, and the total gas flow rate is 50sccm. The etching gas is an Ar+CF4 combination gas; the introduction of fluorine-based gas is more beneficial for modifying the Si3N4 sidewall material.The ion beam incident at a second target angle modifies the transition surface morphology. Utilizing ion beam collimation, the top rounded corners of the sidewalls are smoothed, achieving fine-tuning of sidewall rounded corner undulations. This results in complete removal of the rounded corners at the sidewall shoulders, giving the sidewalls a near-standard square shape with an overall top undulation ≤3nm. Adjacent sidewalls exhibit high symmetry and no odd / even effects. The second target incident angle is 80°, determined by the overall undulation of the sidewall rounded corners after the first etching, which is on the order of 8nm. Based on this 80° second target incident angle, the strong directionality of the ion beam is leveraged to control its low divergence, achieving higher recognition of the undulating surface and ultimately achieving fine smoothing. The grid voltage for the ion beam incident at the second target angle is 1000V, based on the 8nm undulation of the sidewall shoulder rounded corners after the first etching. A 1000V high-energy process is selected to increase the initial kinetic energy of the ion beam and enhance its collimation. Strong directional collimation is used to achieve fine recognition and directional elimination of undulations. The accelerating grid voltage of the ion beam incident at the second target incident angle is 1200V. The ACV (Accumulation Voltage) affects the beam divergence angle and collimation of the ion beam; a higher ACV helps improve collimation and achieve more precise surface undulation shaping. The screen grid current of the ion beam incident at the second target incident angle is 0.2A. A low BMI (Browser Mass Index) results in a low ion density, reducing collisions between ion beams and enhancing beam collimation, which is beneficial for fine-tuning the rounded corners of the sidewall shoulders. The cavity pressure of the ion beam incident at the second target incident angle is set to 0.05mT, and the total gas flow rate is 20sccm. Low cavity pressure helps increase the mean free path of molecules, thereby reducing the probability of collisions between ions, improving beam collimation, and facilitating precise shaping of the target area. The etching gas used for the ion beam incident at the second target incident angle is Ar, an inert gas. Inert gases have higher ion quality, making it easier to control the directionality of the ion beam. Based on a two-stage etching process, the rounded corner morphology of the sidewall shoulders is completely removed, resulting in a near-standard square morphology for the sidewalls. The overall top undulation is ≤3nm, and the adjacent sidewalls exhibit high symmetry, significantly eliminating the parity effect. This provides a technical solution for cross-wafer level, in-situ global modification, achieving high-fidelity transfer of defined patterns, avoiding pattern distortion and potential line collapse, and ultimately improving the expression of device electrical performance.

[0101] The second example illustrates the parity effect caused by sidewall morphology asymmetry in the SAQP process of DRAM memory devices. For the specific process flow of DRAM surface modification using ion beam shaping, please refer to [link / reference]. Figure 11 As shown.

[0102] In DRAM manufacturing, after the mandrel removal step in the SAQP process, the asymmetric rounding morphology of the sidewall shoulders, coupled with the selectivity ratio between the mandrel / sidewall / hard mask layers, leads to distortion in the subsequent sidewall morphology. This, in turn, causes a parity effect, resulting in subsequent etching morphology distortion and device electrical failure. In the SAQP self-aligned quadruple imaging technique, this parity effect manifests as rounded corner morphology on the sidewall shoulders, with a rounding undulation height ≥8nm. Furthermore, the rounded corners of adjacent sidewalls face opposite directions, exhibiting a typical parity effect with high sidewall density. The overall wafer uniformity is characterized by a center height higher than the middle and edge regions. The structures to be modified, from bottom to top, are the substrate, hard mask layer, and sidewalls. The mandrel material is amorphous silicon (a-Si), the sidewall material is silicon nitride (Si3N4), and the hard mask layer is low-temperature deposited silicon oxide (LTO). An ion beam modification process is employed to smooth the top rounded corners of the sidewalls, utilizing the collimation of the ion beam. This achieves precise smoothing of the sidewall rounded corner undulations, completely removing the rounded corners of the sidewall shoulders, resulting in a near-standard square shape. The overall top undulation is ≤1nm, with high symmetry and no odd / even effects between adjacent sidewalls. In the ion beam modification process, the incident angle of the second target is 85°, determined based on the overall undulation of the sidewall rounded corners, which is on the order of 8nm. Based on the 85° incident angle of the second target, the strong directionality of the ion beam is utilized to control its low divergence, achieving higher recognition of the undulating surface and ultimately realizing precise smoothing. The grid voltage of the ion beam incident at the second target incident angle is 800V, based on the 8nm sidewall shoulder rounded corner undulation. The 800V high-energy process is selected, leveraging the high initial kinetic energy of the ion beam to increase its collimation, and utilizing strong directional collimation to achieve precise recognition and directional elimination of undulations. The accelerating grid voltage of the ion beam incident at the second target incident angle is set to 1000V. A high ACV allows for ion beam concentration in the center region, achieving a higher ion beam density in the center region than in the middle and edge regions, resulting in higher etching rates. This optimizes the uniformity of the center region's overall height being higher than that of the middle and edge regions, achieving high uniformity at the wafer level. On the other hand, ACV affects the beam divergence angle and collimation of the ion beam; a high ACV further enhances collimation, enabling more precise surface undulation shaping. The screen current of the ion beam incident at the second target incident angle is 0.5A. A relatively low BMI results in a lower ion density, reducing collisions between ion beams and enhancing beam collimation, which is beneficial for fine-tuning the rounded corners of the sidewall shoulders. The cavity pressure of the ion beam incident at the second target incident angle is set to 0.2 mT, and the total gas flow rate is 40 sccm. The low cavity pressure is conducive to increasing the mean free path of molecules, thereby reducing the probability of collisions between ions, improving the collimation of the ion beam, and facilitating the precise modification of the target area.The etching gas used for the ion beam incident at the second target incident angle is an inert gas, Kr. Kr has higher ion quality and is easier to control the directionality of the ion beam. The ion beam modification process can completely remove the rounded corner morphology of the sidewall shoulders, resulting in a near-standard square morphology for the sidewalls. The overall top undulation is ≤1nm, and there is high symmetry between adjacent sidewalls. This significantly eliminates the parity effect, achieves high-fidelity transfer of the defined pattern, avoids pattern distortion and potential line collapse, and ultimately improves the expression of the device's electrical performance.

[0103] The third example illustrates the parity effect caused by mandrel morphology asymmetry in the SADP process during 3D NAND memory manufacturing. For a detailed process flow of 3D NAND surface modification using ion beam shaping, please refer to [link / reference needed]. Figure 12 As shown.

[0104] In the field of 3D NAND memory manufacturing, after the mandrel removal step in the SADP process, the asymmetric appearance of the rounding morphology at the sidewall shoulders, coupled with the mandrel / sidewall selectivity ratio issue, leads to subsequent sidewall morphology distortion. This, in turn, causes a parity effect, resulting in subsequent etching morphology distortion and device electrical failure. In 3D NAND manufacturing, the parity effect in the SADP self-aligned dual imaging technology manifests as rounded corner morphology at the sidewall shoulders, with a rounding undulation height of 10nm. Furthermore, the rounded corners of adjacent sidewalls face opposite directions, exhibiting a typical parity effect, and the sidewall density is relatively low. The overall wafer uniformity is also affected, with the sidewall height in the Middle region being higher than that in the Center and Edge regions. The structures to be modified, from bottom to top, are the substrate and the sidewalls. The mandrel material is a spin-coated organic layer (OUL), and the sidewall material is silicon nitride (Si3N4). An ion beam finishing process was employed to smooth the top rounded corners of the sidewalls, utilizing the collimation of the ion beam. This achieved the smoothing of the sidewall rounded corner undulations, completely removing the rounded corners of the sidewall shoulders, resulting in a near-standard square shape for the sidewalls. The overall top undulation was ≤3nm, with height symmetry and no odd / even effects between adjacent sidewalls. In the ion beam finishing process, the second target incident angle was 70°, determined based on the 10nm-level overall undulation of the sidewall rounded corners. Based on the 70° second target incident angle, the strong directionality of the ion beam was leveraged to control its low divergence, achieving higher recognition of the undulating surface and ultimately achieving fine smoothing. The grid voltage for the ion beam incident at the second target incident angle was set to 600V, based on the 10nm sidewall shoulder rounded corner undulation. Choosing the 600V process balanced the overall height loss of the sidewalls with the relatively high initial ion beam kinetic energy, increasing the collimation of the ion beam. The strong directional collimation enabled fine recognition and directional elimination of undulations, ultimately resulting in a significant improvement in the rounding of the sidewall shoulders. The accelerating grid voltage of the ion beam incident at the second target incident angle is 600V. This ACV setting allows the ion beam to be concentrated in the middle region, achieving a higher ion beam density in the middle region than in the center and edge regions. This results in a higher etching rate and optimizes the uniformity of the overall height of the middle region compared to the center and edge regions, achieving high uniformity at the wafer level. Furthermore, a relatively high ACV helps improve the collimation of the ion beam, enabling more precise directional smoothing of surface undulations. The screen grid current of the ion beam incident at the second target incident angle is 0.2A. The low BMI results in a low ion density, reducing collisions between ion beams, enhancing beam collimation, and improving the ion beam's directional recognition capability. This facilitates the fine finishing of the rounded corner undulations on the sidewall shoulders.The cavity pressure of the ion beam incident at the second target incident angle is set to 2 mT, and the total gas flow rate is 80 sccm. The relatively low cavity pressure is beneficial for increasing the mean free path of molecules, reducing the probability of collisions between ions, improving the collimation of the ion beam, and facilitating precise modification of the target area. The etching gas for the ion beam incident at the second target incident angle is Kr+CHF3, an inert gas and a fluorine-based gas. Kr has a higher ion quality and is easier to control the directionality of the ion beam. The introduction of fluorine-based gas is more conducive to the modification of the sidewall material Si3N4. The etching gas with a high selectivity between the sidewall and the substrate is preferred. The ion beam modification process can completely remove the rounded corner morphology of the sidewall shoulders, resulting in a near-standard square morphology of the sidewalls. The overall top undulation is ≤3nm, and the adjacent sidewalls exhibit high symmetry. This provides a technical solution for cross-wafer level, in-situ global modification, which greatly eliminates the parity effect, achieves high-fidelity transfer of defined patterns, avoids pattern distortion and potential line collapse, and ultimately improves the expression of device electrical performance.

[0105] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. A method for manufacturing a semiconductor structure, characterized in that, The method includes: A first surface morphology of a structure to be modified is obtained. The structure to be modified includes a substrate and a plurality of sidewalls located on one side of the substrate. The first surface morphology of the structure to be modified includes at least the following: the side surface of the sidewall away from the substrate is an inclined surface; the inclined surface and the surface of the substrate are at a fixed angle; the side surface of the sidewall away from the substrate and the sidewall surface of the sidewall form a rounded corner shape; and the inclined directions of the inclined surfaces of adjacent sidewalls are opposite. The target incident direction of the ion beam is determined according to the arrangement direction of the multiple sidewalls, and the target incident angle of the ion beam along the target incident direction is determined according to the first surface morphology of the structure to be modified and the sidewall density of the multiple sidewalls. An ion beam etching process is used to etch the structure to be modified at a target incident angle along the target incident direction, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology. The second surface morphology includes at least the following: the sidewall away from the substrate is a flat surface parallel to the substrate surface; the inclined surface and the substrate surface form a target angle; the sidewall away from the substrate and the sidewall surface form a right angle; and the flat surfaces of adjacent sidewalls are axially symmetrical. The target angle is less than the fixed angle.

2. The method according to claim 1, characterized in that, The first surface morphology of the structure to be modified includes the undulation difference of the inclined surface; the undulation difference is the difference between the highest point and the lowest point in the inclined surface; The step of determining the target incident direction of the ion beam based on the arrangement direction of the plurality of sidewalls, and determining the target incident angle of the ion beam based on the first surface morphology of the structure to be modified and the sidewall density of the plurality of sidewalls, includes: The target incident direction of the ion beam is the arrangement direction parallel to the plurality of sidewalls; The target incident angle of the ion beam along the target incident direction is determined based on the difference in undulation of the inclined surface or the sidewall density of the multiple sidewalls.

3. The method according to claim 2, characterized in that, Determining the target incident angle of the ion beam along the target incident direction based on the first surface morphology of the structure to be modified or the sidewall density of the plurality of sidewalls includes: If the sidewall density is greater than the target density or the difference in undulation of the inclined surface is less than or equal to the first difference in undulation, the second target incident angle of the ion beam along the target incident direction is determined according to the first surface morphology of the structure to be modified. The step of using an ion beam etching process to emit an ion beam at a target incident angle along the target incident direction to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, includes: An ion beam is emitted at a second target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, wherein the undulation difference of the smooth surface included in the second surface morphology is less than the undulation threshold.

4. The method according to claim 2, characterized in that, The step of determining the target incident direction of the ion beam based on the arrangement direction of the plurality of sidewalls, determining the target incident angle of the ion beam along the target incident direction based on the first surface morphology of the structure to be modified or the sidewall density of the plurality of sidewalls, and using an ion beam etching process to emit an ion beam at the target incident angle along the target incident direction to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a second surface morphology, includes: If the sidewall density is less than the target density or the difference in undulation of the inclined surface is greater than the first difference in undulation, the first target incident angle of the ion beam is determined according to the first surface morphology of the structure to be modified. The target incident direction of the ion beam is the arrangement direction parallel to the plurality of sidewalls; the ion beam is emitted at a first target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the first surface morphology of the structure to be modified into a transition surface morphology. The second target incident angle of the ion beam along the target incident direction is determined based on the transition surface morphology of the structure to be modified. An ion beam is emitted at a second target incident angle along the target incident direction using an ion beam etching process to etch the structure to be modified, thereby modifying the transition surface morphology of the structure to be modified into a second surface morphology.

5. The method according to claim 4, characterized in that, The incident angle of the first target is smaller than that of the second target.

6. The method according to claim 5, characterized in that, The angle range of the incident angle of the first target is 0°-40°.

7. The method according to claim 3 or 6, characterized in that, The angle range of the second target incident angle is 60°-90°.

8. The method according to claim 4, characterized in that, The first grid voltage of the ion beam emitted at the first target incident angle is less than the second grid voltage of the ion beam emitted at the second target incident angle.

9. The method according to claim 8, characterized in that, The voltage range of the first grid voltage for the ion beam incident at the first target incident angle is 50V-800V, and the voltage range of the second grid voltage for the ion beam incident at the second target incident angle is 500V-1500V.

10. The method according to any one of claims 3-6, characterized in that, The first fluctuation difference is 15nm, and the fluctuation threshold is 5nm.

11. The method according to any one of claims 1-9, characterized in that, A hard mask layer is disposed between the substrate and the sidewall.

12. The method according to claim 11, characterized in that, The hard mask layer is made of dielectric or metallic materials. The dielectric material is silicon nitride, silicon oxide, or silicon oxynitride, and the metallic material is Ta, W, TiN, or TaN. The sidewalls are made of dielectric materials, which are silicon nitride, silicon oxide, low-temperature silicon oxide, or silicon oxynitride.

13. The method according to any one of claims 1-9, characterized in that, The voltage range of the accelerating grid voltage for the ion beam incident at the first target incident angle is 50-1000V, and the voltage range of the accelerating grid voltage for the ion beam incident at the second target incident angle is 500-1500V.

14. The method according to any one of claims 1-9, characterized in that, The range of the grid current for the ion beam incident at the first or second target incident angle is 0.1-1.0A.

15. The method according to any one of claims 1-9, characterized in that, The cavity pressure range for the ion beam incident at the first or second target incident angle is 0.01 mT-5 mT, and the total gas flow rate range for the ion beam incident at the first or second target incident angle is 5 sccm-100 sccm.

16. The method according to any one of claims 1-9, characterized in that, The etching gas for the ion beam incident at the first target incident angle is one or more of inert gas, fluorine-based gas and chlorine-based gas, and the etching gas for the ion beam incident at the second target incident angle is an inert gas.

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