Fin structure of vertical field-effect transistor and its manufacturing method

Abstract

A fin structure for a vertical field-effect transistor (VFET) and a method thereof are provided. The method includes: forming a plurality of mandrels on a substrate, with at least one first gap between the mandrels; forming a plurality of first spacers on side surfaces of the mandrels, such that at least one second gap smaller than the first gap is formed between the first spacers; forming second spacers on side surfaces of the first spacers; removing the mandrels and the first spacers, retaining the second spacers; removing a predetermined portion of the second spacers, such that the remaining second spacers have a two-dimensional shape in a top view; and removing a portion of the substrate not below the remaining second spacers and the remaining second spacers, such that the portion of the substrate below the remaining second spacers forms the fin structure.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 862,829, filed June 18, 2019, with the USPTO, entitled "SEMICONDUCTOR PROCESS FOR 2D FIN FABRICATION," and U.S. Application No. 16 / 775,550, filed January 29, 2020, entitled "FIN STRUCTURE FOR VERTICAL FIELD EFFECT TRANSISTOR HAVING TWO-DIMENSIONAL SHAPE IN PLAN VIEW," the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The apparatus and method consistent with exemplary embodiments of the inventive concept relates to a fin structure having a two-dimensional (2D) shape in a top view of a vertical field-effect transistor (VFET), and more specifically, to a method for manufacturing the fin structure and the fin structure manufactured by the method. Background Technology

[0004] In a VFET, unlike existing planar FETs or finFETs, current flows through a channel formed in a fin-like structure that protrudes vertically from the substrate. The vertically protruding fin-like structure is surrounded by a gate structure, and bottom source / drain (S / D) regions and top S / D regions are formed around the bottom and top of the fin-like structure, respectively.

[0005] Despite the known advantages of VFET devices, including VFETs, compared to existing planar FET or finFET devices, such as high-density structures with reduced size, there is still a need for more improved VFET structures and improved methods for manufacturing such VFETs. Summary of the Invention

[0006] Various embodiments of the present invention provide methods for manufacturing fin structures having a 2D shape in a top view for VFETs, and the fin structures of VFETs manufactured by these methods.

[0007] According to one aspect of an exemplary embodiment, a method for manufacturing a fin structure for a VFET is provided, the method comprising: forming a plurality of mandrels on a substrate, the mandrels having at least one first gap between them; forming a plurality of first spacers on side surfaces of the mandrels respectively, such that at least one second gap smaller than the first gap is formed between the first spacers; forming second spacers on side surfaces of the first spacers; removing the mandrels and the first spacers, retaining the second spacers; removing a predetermined portion of the second spacers such that the remaining second spacers have a two-dimensional (2D) shape in a top view; and removing a portion of the substrate not below the remaining second spacers and the remaining second spacers such that the portion of the substrate below the remaining second spacers forms the fin structure.

[0008] According to another aspect of an exemplary embodiment, a method for manufacturing a fin structure for a VFET is provided, the method comprising: forming a plurality of mandrels on a substrate, having at least one first gap between the mandrels; forming a plurality of first spacers on side surfaces of the mandrels respectively, such that at least one second gap smaller than the first gap is formed between the first spacers; forming second spacers on side surfaces of the first spacers; removing the mandrels and the first spacers, retaining the second spacers, and using the second spacers as a hard mask layer to remove a portion of the substrate not below the second spacers; and removing the second spacers such that the portion of the substrate below the second spacers forms the fin structure.

[0009] According to another aspect of an exemplary embodiment, a fin structure having a 2D shape in a top view is provided for a VFET, wherein the fin structure includes a plurality of straight sections having the same width. Attached Figure Description

[0010] The above and other aspects of the inventive concept will become more apparent to those skilled in the art through a detailed description of exemplary embodiments with reference to the accompanying drawings, wherein:

[0011] Figures 1A to 1E The top view illustrates a method for manufacturing the fin structure of a VFET according to an embodiment;

[0012] Figures 2A to 2F The top view illustrates another method for manufacturing the fin structure of the VFET according to an embodiment;

[0013] Figures 3A to 3F The top view illustrates another method for manufacturing the fin structure of the VFET according to an embodiment. Detailed Implementation

[0014] Various embodiments of the inventive concept will be described more fully below with reference to the accompanying drawings. These embodiments are exemplary and can be implemented in many different forms, and should not be construed as limiting the inventive concept. Rather, these embodiments are provided only to make this disclosure thorough and complete, and to fully convey the inventive concept to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of various layers and regions may be exaggerated; therefore, the drawings are not necessarily drawn to scale, and some features may be exaggerated to show details of particular components or elements. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as representative examples based on teaching those skilled in the art to use the methods and structures of the embodiments in various ways.

[0015] The embodiments provided herein are not excluded from being associated with one or more features of another example or embodiment provided herein or not provided herein but consistent with the inventive concept. For example, even if something described in a particular embodiment is not described in a different embodiment, it may be understood to be related to or combined with the different embodiments, unless otherwise stated.

[0016] For the purposes described below, the terms “upper,” “lower,” “top,” “bottom,” “left,” and “right,” and their derivatives, may be used in relation to the disclosed structures based on context, such as their orientation in the accompanying drawings. The same reference numerals in different drawings may refer to the same structural components or elements thereof.

[0017] It will be understood that when a component or layer is referred to as being "on" another component or layer, "connected to" or "coupled to" another component or layer, it may be directly on, directly connected to or directly coupled to the other component or layer, or there may be intermediate components or intermediate layers. Conversely, when a component is referred to as being "directly on" another component or layer, "directly connected to" or "directly coupled to" another component or layer, there are no intermediate components or intermediate layers.

[0018] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of…” when following a list of elements modify the entire list of elements, not individual elements in the list. Thus, for example, “at least one of A, B, or C” and “A, B, and / or C” both mean A, B, C, or any combination thereof.

[0019] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to limit the inventive concept. Unless the context clearly indicates otherwise, the singular forms (e.g., a, an, or the) used herein are also intended to include the plural forms. It will also be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof.

[0020] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments pertain. It will also be understood that, unless expressly defined herein, terms such as those defined in common dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and shall not be interpreted in an idealized or overly formal sense.

[0021] Although the fins of a VFET protrude from the substrate, when viewed from a top view (i.e., when viewed from above), the fins can also have a one-dimensional (1D) form, such as the character "l" or a straight line. Since the size of the current path, at least, is a factor determining the performance of a VFET, it can be the area of ​​the VFET's fins in the top view; therefore, the effective fin width (W) of a fin structure with a two-dimensional (2D) shape when viewed from a top view is also significant. eff The effective fin width should be larger than that of a 1D fin because the larger area of ​​the 2D fin structure provides a larger current path between the bottom and top S / D regions of the VFET.

[0022] Figures 1A to 1E The top view illustrates a method for manufacturing the fin structure of a VFET according to an embodiment.

[0023] Reference Figure 1A The substrate 100 is provided with a pair of mandrels 110-1 and 110-2 formed thereon. Both mandrels 110-1 and 110-2 may have a rectangular shape and may be symmetrically arranged on the substrate 100 such that the short side of mandrel 110-1 faces the short side of mandrel 110-2 across a gap having a critical dimension (hereinafter referred to as "GAP CD"). GAP CD represents the width between the two facing short sides of mandrels 110-1 and 110-2 and may define the critical dimension of the fin-like structure to be formed according to this embodiment.

[0024] According to the present invention, the shape of each of the mandrels 110-1 and 110-2 is not limited to a rectangle. Furthermore, according to the present invention, the two mandrels 110-1 and 110-2 can be symmetrically arranged on the substrate such that the long sides, rather than the short sides, of the two mandrels 110-1 and 110-2 can face each other.

[0025] Although a cross-sectional view of the substrate 100 having mandrels 110-1 and 110-2 thereon is not shown, mandrels 110-1 and 110-2 can be formed on the substrate 100 by photolithography and etching processes, such that mandrels 110-1 and 110-2 can have a protruding shape extending from the substrate 100. However, the inventive concept is not limited thereto, and mandrels 110-1 and 110-2 can be formed using methods other than photolithography and etching. Furthermore, although in Figures 1A to 1E Although not shown, one or more hard mask layers (not shown) may be provided between the substrate 100 and the mandrels 110-1 and 110-2.

[0026] The substrate 100 may be formed of a single-element semiconductor material such as silicon (Si), germanium (Ge), or a compound thereof (SiGe). The substrate 100 may be a doped or undoped layer. The mandrels 110-1 and 110-2 may be formed of a spin-on hard mask (SOH) material comprising a silicon-based organic material, but are not limited thereto. Various amorphous silicon materials may be used to form the mandrels 110-1 and 110-2, provided that the mandrels 110-1 and 110-2 have etch selectivity relative to the spacers formed on the side surfaces (i.e., sidewalls) of the mandrels 110-1 and 110-2 and above the fin structure in the steps of the method according to this embodiment.

[0027] Figure 1B Spacers 120 are shown formed on the side surfaces of mandrels 110-1 and 110-2. Figure 1B It is also shown that spacer 120 fills the gap with GAP CD between the two short sides of mandrels 110-1 and 110-2 that face each other, such that spacer 120 has a coherent structure and surrounds mandrels 110-1 and 110-2.

[0028] The spacer 120 can be formed by depositing a spacer material such as silicon oxide (SiO) on mandrels 110-1 and 110-2 to cover their top and side surfaces, and etching away the spacer material deposited on the top surface to expose the top surface to the outside, while retaining the spacer material on the side surfaces of mandrels 110-1 and 110-2. It should be noted that the spacer material completely fills the gap with a gap CD between the two short, facing sides of mandrels 110-1 and 110-2.

[0029] The deposition of spacer material can be performed using thin-film deposition techniques such as atomic layer deposition (ALD), but is not limited thereto, so that spacer 120 can have the same width along the side surfaces of mandrels 110-1 and 110-2, which can be the size required for the desired fin structure formed according to this embodiment. According to the concept of the invention, the etching process used in this step can be anisotropic etching or plasma etching, but is not limited thereto.

[0030] The spacer material forming spacer 120 may not be limited to SiO, as long as the spacer material has etch selectivity relative to the materials forming mandrels 110-1 and 110-2.

[0031] Figure 1C The mandrels 110-1 and 110-2 surrounded by spacers 120 are shown to be removed by another etching process such as dry etching (not limited thereto) to retain the spacers 120 formed on the side surfaces of the mandrels 110-1 and 110-2 on the substrate 100.

[0032] Figure 1D The spacer 120 is shown to be cut or etched on two opposite sides along its length to form an H-shaped spacer 130, i.e., the shape of the character "H" with the desired dimensions when viewed from above. It should be noted here that... Figure 1A The GAP CD shown is due to Figures 1A to 1C The photolithography, deposition, and etching processes shown are transformed into the critical dimensions of the H-shaped spacer 130 (hereinafter referred to as "SPACER CD1"). SPACER CD1 of the H-shaped spacer 130 represents the width of the horizontal portion 130H of the H-shaped spacer 130 and can be equal to the GAP CD, which will define the critical dimension of the fin-like structure to be formed in the next step in the top view. Furthermore, the width of the horizontal portion 130H of the H-shaped spacer 130 can be equal to the width of the vertical portion 130V of the H-shaped spacer 130.

[0033] Figure 1E The diagram illustrates the use of an H-shaped spacer 130 as a hard mask layer, etching down onto the substrate 100, and also removing the H-shaped spacer 130 by etching, thereby forming an H-shaped fin structure 140 perpendicular to the substrate 100 and also having the shape of the character "H". A bottom S / D region is then formed in the substrate 100 below the H-shaped fin structure 140. Here, SPACER CD1 becomes the critical dimension of the H-shaped fin structure 140 (hereinafter referred to as "FIN CD1"). Therefore, Figure 1A The GAP CD shown is ultimately transformed into and defines FIN CD1. In other words, FIN CD1 equals Figure 1AThe GAP CD is shown. According to the present invention, the etching process used to obtain the H-shaped fin structure 140 can be dry etching, but is not limited thereto.

[0034] The above references Figures 1A to 1E The above-described embodiments describe a method for fabricating an H-shaped fin structure for a VFET. However, according to embodiments, this method can also be used to fabricate fin structures with different 2D shapes having characters, symbols, or marks such as "E", "X", "+", etc., formed by multiple straight segments. For example, when forming a fin structure with a plus sign "+", the substrate is provided with four rectangular cores, with gaps between the short sides of the four rectangular cores and another gap between their long sides, and spacers are formed on the side surfaces of the cores. Furthermore, the above-described etching process can be used to form the fin structure with the plus sign.

[0035] As described above, in terms of VFET current performance, 2D fin structures have an area advantage compared to 1D fin structures. However, the above embodiments may be insufficient to obtain VFET devices with finer 2D fin structures to achieve high-density VFET devices with improved performance. This is because, although it is desirable to make the FIN CD1 less than 10 nm when forming the VFET fin structure, it is difficult to photolithographically and etch the mandrels 110-1 and 110-2 to have a GAP CD of 10 nm or less, even by extreme ultraviolet (EUV) lithography and etching. Therefore, this embodiment may not be able to achieve this size of the VFET fin structure. Therefore, different methods for fabricating VFET fin structures are provided below.

[0036] Figures 2A to 2F The top view illustrates another method for manufacturing the fin structure of a VFET according to an embodiment. Since the method provided in this embodiment is similar to that of the methods in the preceding embodiments, repeated descriptions can be omitted below.

[0037] and Figure 1A resemblance, Figure 2A A substrate 200 is shown having a pair of rectangular mandrels 210-1 and 210-2 symmetrically formed thereon, such that the short side of mandrel 210-1 faces the short side of mandrel 210-2 across a first gap, which has a first critical dimension in the top view (hereinafter referred to as "GAP CD1"). GAP CD1 represents the width between the two facing short sides of mandrels 210-1 and 210-2. However, it should be noted that, unlike GAP CD in the previous embodiments, GAP CD1 may not limit the critical dimension of the fin structure formed according to this embodiment.

[0038] Similar to the previous embodiments, according to the present invention, the shapes of mandrels 210-1 and 210-2 and their symmetrical positions on the substrate 220 are not limited thereto. Therefore, mandrels 210-1 and 210-2 can have shapes other than rectangles, and their long sides, rather than their short sides, can face each other.

[0039] Furthermore, similar to the previous embodiments, although a cross-sectional view of the substrate 200 having mandrels 210-1 and 210-2 is not shown, mandrels 210-1 and 210-2 can be formed on the substrate 200 by photolithography and etching processes, such that mandrels 210-1 and 210-2 can have a protruding shape extending from the substrate 200. However, according to the present invention, different methods can be used to form mandrels 210-1 and 210-2. Although in Figures 2A to 2F Although not shown, one or more hard mask layers (not shown) may be provided between the substrate 200 and the mandrels 210-1 and 210-2.

[0040] Similar to substrate 100 in the preceding embodiments, substrate 200 may be formed of a single-element semiconductor material such as Si, Ge, etc. (not limited thereto) or a compound thereof (SiGe), and may be doped or undoped. Mandrels 210-1 and 210-2 may also be formed of an SOH material comprising a silicon-based organic material, but are not limited thereto, and various different amorphous silicon materials may be used to form mandrels 210-1 and 210-2, provided that mandrels 210-1 and 210-2 have etch selectivity relative to one or more spacers formed on the side surfaces (i.e., sidewalls) of mandrels 210-1 and 210-2 and above the fin structure in the steps of the method according to this embodiment.

[0041] Figure 2B A first spacer is shown formed on the side surfaces of mandrels 210-1 and 210-2. However, unlike spacer 120 in the previous embodiment, the first spacer does not fill the first gap with GAP CD1 between the two short sides of mandrels 210-1 and 210-2 that face each other. Instead, the first spacer comprises two first spacers 220-1A and 220-1B formed on the side surfaces of mandrels 210-1 and 210-2, respectively. Both first spacers 220-1A and 220-1B have a coherent structure and surround mandrels 210-1 and 210-2. A second gap with a second critical dimension (hereinafter referred to as "GAP CD2") is provided between the two short sides of the two first spacers 220-1A and 220-1B that face each other. This GAP CD2 may define the critical dimension of the fin-like structure formed according to this embodiment.

[0042] The first spacers 220-1A and 220-1B can be formed by depositing a spacer material such as SiO on mandrels 210-1 and 210-2 to cover their top and side surfaces, and etching away the spacer material deposited on the top surface to expose the top surface, while retaining the spacer material on the side surfaces of mandrels 210-1 and 210-2. However, it should be noted that, unlike spacer 120 in the previous embodiment, the spacer material does not completely fill the gap with GAP CD1 between mandrels 210-1 and 210-2, but instead provides a second gap with GAP CD2, which can define the critical dimensions of the fin structure formed according to this embodiment.

[0043] Similar to the previous embodiments, the deposition of spacer material can be performed using thin-film deposition techniques such as ALD, but is not limited thereto, such that the first spacers 220-1A and 220-1B can each have the same width along the side surfaces of the mandrels 210-1 and 210-2, respectively. It should be noted that, due to thin-film deposition techniques such as ALD, it can be ensured that the GAP CD2 is smaller than GAP CD1 to define the fin-like structure formed according to this embodiment. Similar to the previous embodiments, the etching process used herein to remove the spacer material deposited on the top surfaces of the mandrels 210-1 and 210-2 can be anisotropic etching or plasma etching, but is not limited thereto.

[0044] The spacer material forming the first spacer may not be limited to SiO, as long as it has etch selectivity relative to the material forming the other spacer, which will be formed on the first spacer and mandrels 210-1 and 210-2 in subsequent steps of this embodiment. However, according to this embodiment, the spacer material forming the first spacer may or may not have etch selectivity relative to the materials forming mandrels 210-1 and 210-2.

[0045] Figure 2C A second spacer 220-2 is formed on the side surfaces of the first spacers 220-1A and 220-1B. Figure 2C It is also shown that the second spacer 220-2 fills the gap with GAP CD2 between the two short sides of the first spacers 220-1A and 220-1B that face each other, so that the second spacer 220-2 has a coherent structure.

[0046] The second spacer 220-2 can be formed by depositing a spacer material, such as polysilicon, on the mandrels 210-1 and 210-2 and the first spacers 220-1A and 220-1B to cover the top surfaces of the mandrels 210-1 and 210-2, the top surfaces of the first spacers 220-1A and 220-1B, and the side surfaces of the first spacers 220-1A and 220-1B, and etching away the spacer material deposited on the top surfaces of the mandrels 210-1 and 210-2 and the top surfaces of the first spacers 220-1A and 220-1B to expose them to the outside, while retaining the spacer material on the side surfaces of the first spacers 220-1A and 220-1B. It should be noted that the second spacer 220-2 completely fills the gap with GAP CD2 between the two facing short sides of the first spacers 220-1A and 220-1B.

[0047] The process of depositing spacer material to form the second spacer 220-2 can be the same as the above reference. Figure 2B The process described for forming the first spacers 220-1A and 220-1B is the same thin film deposition technique as ALD (but not limited thereto), so that the second spacer 220-2 can have the same width along the side surfaces of the first spacers 220-1A and 220-1B, which can be the size required for the desired fin structure formed according to this embodiment. The etching process used in this step to remove the spacer material deposited on the top surfaces of the first spacers 220-1A and 220-1B and the top surfaces of the mandrels 210-1 and 210-2 can be referenced. Figure 2B Anisotropic etching or plasma etching, but not limited to, is used when forming the first spacers 220-1A and 220-1B.

[0048] The spacer material forming the second spacer 220-2 may not be limited to polysilicon, as long as the spacer material has etch selectivity relative to the materials forming the mandrels 210-1 and 210-2 and the spacer materials forming the first spacers 220-1A and 220-1B.

[0049] Figure 2D The removal of mandrels 210-1 and 210-2 by another etching process, such as dry etching (but not limited to this), is shown. Figure 2C The first spacers 220-1A and 220-1B formed on the side surfaces of the mandrels 210-1 and 210-2 are shown to retain the second spacer 220-2 formed on the side surfaces of the first spacers 220-1A and 220-1B on the substrate 100.

[0050] Figure 2EThe second spacer 220-2 is shown to be cut or etched on two opposite sides along its length to form an H-shaped spacer 230 similar to the H-shaped spacer 130 in the previous embodiment. This H-shape is identical in shape to the fin-like structure to be formed herein in a top view. It should be noted here that... Figure 2B The GAP CD2 shown is due to Figures 2A to 2D The photolithography, deposition, and etching processes shown are transformed into the critical dimensions of the H-shaped spacer 230 (hereinafter referred to as "SPACER CD2"). SPACERCD2 represents the width of the horizontal portion 230H of the H-shaped spacer 230 and can be equal to the GAP CD2 that will define the critical dimensions of the fin-like structure to be formed in the next step. Furthermore, the width of the horizontal portion 230H of the H-shaped spacer 230 can be equal to the width of the vertical portion 230V of the H-shaped spacer 230.

[0051] Figure 2F It is shown that, using an H-shaped spacer 230 as a hard mask layer, portions of the substrate 200 are etched downwards, except for those located below the H-shaped spacer 230, and the H-shaped spacer 230 is also removed by etching, thereby forming an H-shaped fin structure 240 perpendicular to the substrate 200 and also having the shape of the character "H". A bottom S / D region is then formed in the substrate 200 below the H-shaped fin structure 240. Here, SPACER CD2 becomes a critical dimension of the H-shaped fin structure 240 (hereinafter referred to as "FIN CD2"). Therefore, Figure 2B The GAP CD2 shown ultimately transforms into and defines FIN CD2. In other words, the FIN CD2 of the H-shaped fin structure 240 is equal to Figure 2B The GAP CD2 is shown. According to the present invention, the etching process used to obtain the H-shaped fin structure 240 can be dry etching, but is not limited thereto.

[0052] The above references Figures 2A to 2F In the described embodiment, another H-shaped fin structure for the VFET was fabricated. However, as described in the preceding embodiments, the inventive concept can also be used to fabricate fin structures with different 2D shapes, such as characters or symbols “E”, “X”, “+”, etc.

[0053] It should be noted that while the previous embodiments used a single spacer (e.g., spacer 120) to form a fin structure with a 2D shape (e.g., a character H-shape), this embodiment uses two different spacers (e.g., a first spacer and a second spacer) to form a fin structure with the same 2D shape. Furthermore, although the previous embodiments could not form fin structures with a critical size of 10 nm or less in a top view due to the difficulty in photolithographically etching the mandrel to have a small gap critical size on the substrate, this embodiment is able to form such a fin structure because the first spacer with the smaller gap critical size among the two different spacers can be formed on the substrate, thereby achieving a VFET with improved performance.

[0054] The above references Figures 2A to 2F The above-described embodiments describe another method for fabricating an H-shaped fin structure for a VFET. However, according to the embodiments, this method, similar to that in the preceding embodiments, can also be used to fabricate fin structures with different 2D shapes having characters, symbols, or marks such as “E,” “X,” “+,” etc., formed by multiple straight segments. For example, when forming a fin structure with a plus sign “+,” the substrate is provided with four rectangular cores, the short sides of which have a first gap and the long sides have another first gap, and a plurality of first spacers are formed on the side surfaces of the cores, the short sides of which have a second gap and the long sides have another second gap. Furthermore, second spacers are formed on the side surfaces of the first spacers to completely fill the second gaps, and the fin structure with the plus sign can be formed using the etching process described above.

[0055] Furthermore, in the above embodiments, rectangular mandrels are used to manufacture the H-shaped fin structure. Each mandrel can have a rounded rectangular shape, that is, each vertex of the rectangular mandrel is rounded. Therefore, the subsequently formed spacers can also have a rounded rectangular shape. Thus, the fin structure formed using these rounded rectangular mandrels and spacers may not have a precise H-shape, but rather a circular or deformed H-shape as described below.

[0056] Figures 3A to 3F The top view illustrates another method for manufacturing the fin structure of the VFET according to an embodiment.

[0057] Figures 3A to 3FA fin-like structure 340 with a circular or deformed H character is shown, formed using a pair of mandrels 310-1 and 310-2, each having rounded rectangles, and a pair of first spacers 320-1A and 320-1B. Furthermore, in this embodiment, the second spacer 320-2 has the shape of two connected rounded rectangles. Also, as in the previous embodiments, the same GAP CD1 is provided between the mandrels 310-1 and 310-2, the same GAPCD2 is provided between the first spacers 320-1A and 320-1B, the same SPACER CD2 is provided, and the same FIN CD2 is provided.

[0058] It should be noted that the reason for forming rounded rectangles is that when the mandrels 310-1 and 310-2 are formed on the substrate 300, they can be rounded rectangles rather than precise rectangles; and by using thin film deposition techniques such as ALD (but not limited to) to form the first spacers 320-1A and 320-1B and the second spacer 320-2, the corresponding materials can be conformally deposited on the side surfaces of the mandrels 310-1 and 310-2 and the side surfaces of the first spacers 320-1A and 320-1B, respectively. Therefore, as Figure 3B and 3C As shown, the straight portion A and the rounded portion B of the first spacer 320-1A can have the same width, and the straight portion C and the rounded portion D of the second spacer 320-2 can also have the same width, which can be equal to the critical dimension of the rounded H-shaped spacer 330, which is subsequently equal to the critical dimension of the rounded H-shaped fin structure 340 in the top view. Furthermore, as... Figure 3F The straight portion E and the rounded portion F of the rounded H-shaped fin structure 340 shown can have the same width. Therefore, the rounded H-shaped fin structure 340 can have better current path performance than the H-shaped fin structure 240.

[0059] The materials and processes used to form the mandrels 310-1, 310-2, the first spacers 320-1A, 320-1B, the second spacer 320-2, the rounded H-shaped spacer 330, and the rounded H-shaped fin structure 340 may be the same as or similar to those used in the preceding embodiments; therefore, repeated descriptions are omitted here.

[0060] It should be understood that the above can be used as a reference. Figures 1A to 1E , Figures 2A to 2F and Figures 3A to 3F Additional steps are provided before, during, and after the described steps. For additional embodiments of the inventive concept, one or more of the above steps, or a portion thereof, may be replaced, skipped, removed, or moved.

[0061] For example, when forming a fin-like structure with spacers 220-2, the process can be skipped. Figure 2E The steps, and can be in Figure 2D Execute in the steps Figure 2F The process involves using H-shaped spacers 230 as a hard mask layer to etch the substrate 200 downwards. In other words, after removing mandrels 210-1 and 210-2 and spacers 220-1A and 220-1B, spacer 220-2 can be used as a hard mask layer to etch the substrate 200 downwards before removing spacer 220-2 to form a fin structure with the shape of spacer 220-2. This method can be used when forming fin structures with different 2D shapes, such as plus signs, on the substrate using four mandrels.

[0062] The foregoing is a description of exemplary embodiments and should not be construed as limiting them. Although some exemplary embodiments have been described, those skilled in the art will readily understand that many modifications can be made to the above embodiments without substantially departing from the inventive concept.

Claims

1. A method for fabricating a fin structure for a vertical field-effect transistor, the method comprising: A plurality of mandrels are formed on a substrate, with at least one first gap between the mandrels; A plurality of first spacers are formed on the side surface of the mandrel, such that at least one second gap smaller than the first gap is formed between the first spacers; A second spacer is formed on the side surface of the first spacer; Remove the mandrel and the first spacer, leaving the second spacer; Remove a predetermined portion of the second spacer so that the remaining second spacer has a two-dimensional shape in the top view; as well as Remove the portion of the substrate not below the remaining second spacer and the remaining second spacer, such that the portion of the substrate below the remaining second spacer forms the fin structure.

2. The method according to claim 1, wherein, The width of the second gap is equal to the width of the portion of the second spacer formed on one of the side surfaces of the first spacer. The width of the second gap is equal to the width of the portion of the substrate below the remaining second spacer that forms the fin structure.

3. The method according to claim 2, wherein, The formation of the first spacer on the side surface is performed by atomic layer deposition.

4. The method according to claim 1, wherein, Forming the second spacer on the side surface of the first spacer is performed such that: the width of the second spacer is the same along the side surface of the first spacer, and the second gap is completely filled by the second spacer.

5. The method according to claim 1, wherein, The removal of the portion of the substrate not below the remaining second spacer includes: using the remaining second spacer as a hard mask layer, etching downwards the portion of the substrate not below the remaining second spacer.

6. The method according to claim 1, wherein, The formation of the first spacer on the side surface of the mandrel includes: The first spacer is formed on the top surface and the side surface of the mandrel; and The portion of the first spacer located on the top surface of the mandrel is etched, such that the remaining portion of the first spacer remains on the side surface of the mandrel, and the top surface of the mandrel is exposed to the outside.

7. The method according to claim 6, wherein, The formation of the second spacer on the side surface of the first spacer includes: The second spacer is formed on the top surface of the mandrel and on the top and side surfaces of the first spacer; and The portion of the second spacer located on the top surface of the mandrel and the top surface of the first spacer is etched, such that the remaining portion of the second spacer remains on the side surface of the first spacer.

8. The method according to claim 7, wherein, The second spacer is formed of a material that has etch selectivity relative to the material forming the mandrel and the first spacer.

9. The method according to claim 8, wherein, The materials forming the second spacer, the first spacer, and the mandrel have etch selectivity relative to each other.

10. The method according to claim 9, wherein, The material forming the mandrel includes a spin-coated hard mask material comprising a silicon-based organic material. The material forming the first spacer includes silicon oxide. The material forming the second spacer includes polycrystalline silicon.

11. The method according to claim 1, wherein, The second spacer comprises multiple straight sections of the same width.

12. The method according to claim 11, wherein, The width of the second gap is equal to the same width.

13. The method according to claim 1, wherein, Each of the aforementioned mandrels is a rounded rectangle. The first spacer is conformally formed on the side surface of the mandrel such that the first spacer has the same width in a top view. The second spacer is conformally formed on the side surface of the first spacer, such that the rounded corner portion and the straight portion of the second spacer have the same width.

14. A method for fabricating a fin structure for a vertical field-effect transistor, the method comprising: A plurality of mandrels are formed on a substrate, with at least one first gap between the mandrels; A plurality of first spacers are formed on the side surface of the mandrel, such that at least one second gap smaller than the first gap is formed between the first spacers; A second spacer is formed on the side surface of the first spacer; Remove the mandrel and the first spacer, retain the second spacer, and use the second spacer as a hard mask layer to remove the portion of the substrate that is not below the second spacer; as well as Remove the second spacer so that the portion of the substrate below the second spacer forms the fin structure.

15. The method according to claim 14, wherein, The width of the second gap is equal to the width of the second spacer formed on one of the side surfaces of the first spacer.

16. The method of claim 14, wherein, Each of the aforementioned mandrels is a rounded rectangle. The first spacer is conformally formed on the side surface of the mandrel such that the first spacer has the same width in a top view. The second spacer is conformally formed on the side surface of the first spacer, such that the rounded corner portion and the straight portion of the second spacer have the same width in the top view.

Images