Manufacturing method of semiconductor device
By using the technique of patterning mask layer and multiple second openings in the semiconductor device manufacturing process, the problem of unpredictability of the bird beak structure during the local silicon oxide formation process is solved, and the controllable morphology and area of the bird beak structure are achieved, and the device performance and miniaturization ability are improved.
Patent Information
- Application Number
- CN202311441446.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-01
- Publication Date
- 2025-05-06
AI Technical Summary
In the prior art, there is unpredictability of the bird beak structure during the formation of local silicon oxide, which affects subsequent process control and device performance, and the existing methods cannot effectively control the morphology and area of the bird beak structure.
By forming a pad oxide layer and a hard mask layer on the substrate, the first opening is formed, and a plurality of second openings are formed outside the first opening mask layer masking the first opening, the line width of the second opening gradually decreases in a direction away from the first opening, and the formation of local oxides is controlled by these second openings to ensure that the morphology of the beak structure is controllable and the area is reduced.
It is realized that the morphology and area of the beak structure is controlled without reducing the thickness of the pad oxide layer and the local silicon oxide thickness, so as to improve the device performance and facilitate the miniaturization of the device.
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Figure CN119943746A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor device manufacturing, and in particular to a method for manufacturing a semiconductor device. Background Art
[0002] One method of forming a device isolation structure in the prior art is the local oxidation of silicon (LOCOS) isolation process. Figure 1 In the LOCOS isolation process, a pad oxide layer 101 (Pad Oxide) is formed on the surface of the substrate 100 and a silicon nitride layer 102 is deposited. Then, a portion of the silicon nitride layer 102 and the pad oxide layer 101 are etched away to expose a portion of the substrate 100. The exposed substrate 100 is thermally oxidized to generate a local silicon oxide 103. The substrate 200 in the area covered by the silicon nitride layer 102 around the local silicon oxide 103 is used as the active area AA for manufacturing active devices. In this way, different active devices are isolated by the local silicon oxide 103. The local silicon oxide 103 formed by the LOCOS isolation process usually has a large thickness and can achieve a good isolation effect, so it can be used in high-voltage device processes.
[0003] However, when generating the local silicon oxide 103, some oxygen atoms will perform lateral incursion into the substrate 200 in the area covered by the silicon nitride layer 102, so that the substrate 200 below the edge area of the silicon nitride layer 102 is oxidized to form a bird's beak structure 103a. The existence of the bird's beak structure 103a will increase the area occupied by the local silicon oxide 103, and the morphology of the bird's beak structure 103a is unpredictable, which will have an adverse effect on the subsequent process control and the subsequently formed devices.
[0004] In the prior art, the bird's beak effect is usually reduced by reducing the thickness of the pad oxide layer 101 or reducing the thickness of the local silicon oxide 103. However, reducing the thickness of the pad oxide layer 101 will affect the stress relief effect of the pad oxide layer 101 on the silicon nitride layer 102 and the substrate 100, and reducing the thickness of the local silicon oxide 103 will affect the isolation effect of the device, and these two methods still cannot make the morphology of the bird's beak structure 103a controllable.
[0005] Therefore, a new technical solution is needed that can make the morphology of the bird's beak structure controllable and reduce the occupied area without reducing the thickness of the pad oxide layer and the thickness of the formed local silicon oxide itself when forming local silicon oxide, thereby improving device performance and facilitating device miniaturization. Summary of the invention
[0006] The object of the present invention is to provide a method for manufacturing a semiconductor device, which can make the morphology of the bird's beak structure controllable and reduce the occupied area without reducing the thickness of the pad oxide layer and the thickness of the formed local silicon oxide itself when forming local silicon oxide, thereby improving device performance and facilitating device miniaturization.
[0007] To achieve the above object, the present invention provides a method for manufacturing a semiconductor device, which comprises the following steps:
[0008] providing a substrate, and forming a pad oxide layer and a hard mask layer on the substrate;
[0009] etching the hard mask layer and the pad oxide layer to form a first opening exposing a local area of the substrate;
[0010] Forming a patterned mask layer, wherein the patterned mask layer masks the first opening, and a plurality of second openings are formed in the area outside the first opening, and the line width of the second openings gradually decreases along a direction away from the first opening;
[0011] Using the patterned mask layer as a mask, etching the hard mask layer at the bottom of each second opening to deepen each second opening to a desired depth, wherein the bottom of each deepened second opening does not expose the pad oxide layer;
[0012] The patterned mask layer is removed, and the substrate exposed by the first opening and the substrate under the second opening are thermally oxidized, so that the oxide layer formed at the first opening and the oxide layers formed at each second opening outside the first opening are connected together to form a local oxide.
[0013] Optionally, after forming the pad oxide layer on the substrate and before forming the hard mask layer, an etch stop layer is also formed on the pad oxide layer; when etching the hard mask layer at the bottom of each second opening using the patterned mask layer as a mask, the etching stops at the top surface or corresponding depth of the etch stop layer.
[0014] Optionally, after forming the pad oxide layer on the substrate and before forming the hard mask layer, the thickness of the etch stop layer formed on the pad oxide layer is Alternatively, after deepening each of the second openings to a desired depth, the thickness of the etching stop layer remaining at the bottom of the second opening is
[0015] Optionally, when etching the hard mask layer and the pad oxide layer to form the first opening, the hard mask layer is first dry-etched, and then the etch stop layer and the pad oxide layer are wet-etched until the top surface of the substrate is exposed.
[0016] Optionally, at any step node after forming the patterned mask layer and before thermally oxidizing the substrate exposed by the first opening and the substrate below the second opening, ions for suppressing the oxidation rate of the substrate are injected into the substrate below the second opening using the patterned mask layer as a mask; and / or, at any step node before thermally oxidizing the substrate exposed by the first opening, ions for increasing the oxidation rate of the substrate are injected into the substrate at the first opening.
[0017] Optionally, the ions for suppressing the oxidation rate of the substrate include nitrogen ions, and / or the ions for increasing the oxidation rate of the substrate include at least one of oxygen ions, amorphization ions and halogen ions.
[0018] Optionally, on each side of the first opening, the intervals between the second openings gradually decrease along a direction away from the first opening.
[0019] Optionally, on each side of the first opening, along a direction close to the first opening, a line width of any second opening is the same as a spacing between any second opening and its adjacent second opening.
[0020] Optionally, on each side of the first opening, along a direction close to the first opening, a line width of any second opening is the same as a spacing between the any second opening and its adjacent second opening.
[0021] Optionally, on each side of the first opening, the line width of the innermost second opening is 120 nm to 500 nm, and the line width of the outermost second opening is 80 nm to 200 nm.
[0022] Optionally, on each side of the first opening, an interval between adjacent second openings is 80 nm to 200 nm.
[0023] Optionally, the size of the first opening is smaller than the size of the local oxide to be formed, and after thermal oxidation of the substrate exposed by the first opening and the substrate under the second opening, the size of the local oxide actually formed reaches the size of the local oxide to be formed.
[0024] Optionally, after forming the local oxide, the manufacturing method further includes: etching and removing the oxide layer under at least a portion of the second opening including the outermost second opening according to the outer edge position of the first opening and the position of the outermost second opening, so as to reduce or remove the bird's beak structure of the local oxide.
[0025] Compared with the prior art, the technical solution of the present invention, after etching the hard mask layer to form a first opening exposing a local area of the substrate to be oxidized, uses a patterned mask layer to mask the first opening, and forms a plurality of second openings in the area of the patterned mask layer located outside the first opening, so that when the hard mask layer is etched with the patterned mask layer as a mask, the second opening is transferred to the hard mask layer, and the line width of the second opening gradually decreases in the direction away from the first opening. When the patterned mask layer is removed and the substrate at the first opening is thermally oxidized, the second opening can be used to accurately control the size of the bird's beak of the formed local oxide, so that the bird's beak is as small and thin as possible. The principle is as follows: on the one hand, a small part of oxygen will diffuse downward from the second opening into the substrate to form an oxide layer, and the oxide layer formed at the first opening and the oxide layers formed at the second openings outside the first opening are connected together to form a local oxide, which can ensure that the lateral length of the formed local oxide meets the device manufacturing requirements; on the other hand, since the line width of the second opening on each side of the first opening gradually decreases in the direction away from the first opening, the amount of oxygen passing through the second opening can be reduced in the direction away from the first opening, and the oxide layer formed under each second opening can serve as a multi-layer barrier layer to prevent the oxygen diffused laterally from the first opening from continuing to diffuse outward, thereby accurately controlling the lateral size of the oxide layer formed outside each side of the first opening, and then accurately controlling the bird's beak size of the local oxide, making its bird's beak as small and thin as possible.
[0026] In addition, after the local oxide is formed, the oxide layer under at least a portion of the second opening including the outermost second opening can be etched away according to the outer edge position of the first opening and the position of the outermost second opening, thereby reducing or removing the bird's beak structure of the local oxide. Obviously, the bird's beak structure removal process will be relatively more controllable and reliable because it has the position parameters of the first opening and the outermost second opening as a reference. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.
[0028] Figure 1 It is a cross-sectional schematic diagram of local silicon oxide and its bird's beak structure manufactured by prior art.
[0029] Figure 2 It is a flow chart of a method for manufacturing a semiconductor device according to a specific embodiment of the present invention.
[0030] Figures 3 to 9 It is a schematic diagram of the cross-sectional structure of a device in a method for manufacturing a semiconductor device according to a specific embodiment of the present invention. DETAILED DESCRIPTION
[0031] In the following description, a large number of specific details are given in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described. It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and the scope of the present invention will be fully conveyed to those skilled in the art. The same reference numerals represent the same elements from beginning to end. It should be understood that when an element is referred to as "connected to", "coupled" other elements, it can be directly connected to other elements, or there can be intervening elements. On the contrary, when an element is referred to as "directly connected to" other elements, there is no intervening element. When used here, the singular forms of "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the term "comprising" is used to identify the presence of features, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.
[0032] The technical solution proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.
[0033] Please refer to Figure 2 An embodiment of the present invention provides a method for manufacturing a semiconductor device, which comprises the following steps:
[0034] S1, providing a substrate, and forming a pad oxide layer and a hard mask layer on the substrate;
[0035] S2, etching the hard mask layer and the pad oxide layer to form a first opening exposing a local area of the substrate;
[0036] S3, forming a patterned mask layer, wherein the patterned mask layer masks the first opening, and forms a plurality of second openings in the area outside the first opening, and the line width of the second openings gradually decreases along a direction away from the first opening;
[0037] S4, using the patterned mask layer as a mask, etching the hard mask layer at the bottom of each second opening to deepen each second opening to a desired depth, wherein the bottom of each deepened second opening does not expose the pad oxide layer;
[0038] S5, removing the patterned mask layer, and thermally oxidizing the substrate exposed by the first opening and the substrate under the second opening, so that the oxide layer formed at the first opening and the oxide layers formed at each second opening outside the first opening are connected together to form a local oxide.
[0039] Please refer to Figure 3 In step S1, first, the provided substrate 200 can be any suitable semiconductor substrate material, such as pure silicon, silicon germanium (SiGe), silicon carbide (SiC) or silicon on insulator (SOI), etc. Then, a material such as silicon oxide is formed on the substrate 200 as a pad oxide layer (PAD OX) 201 by any suitable process such as thermal oxidation, atomic layer deposition or plasma enhanced chemical vapor deposition; then, a material such as silicon oxynitride is deposited on the pad oxide layer 201 by any suitable process such as chemical vapor deposition process to form an etch stop layer 202, and the deposition thickness of the etch stop layer 202 can be optionally 200 %. For example Afterwards, a material such as silicon nitride is deposited on the etch stop layer 202 by any suitable process such as a chemical vapor deposition process to form a hard mask layer 203. The pad oxide layer 200 is used to relieve stress between the composite layer formed by stacking the etch stop layer 202 and the hard mask layer 203 and the substrate 200. The hard mask layer 203 is used as a downward transfer layer of the photoresist pattern in the subsequent process, and as a barrier layer to block the diffusion of oxygen atoms when a local oxide is formed by thermal oxidation in the subsequent process. On the one hand, the etch stop layer 202 is used as an etching stop point when etching the hard mask layer 203 later. On the other hand, its material properties are between the hard mask layer 203 and the pad oxide layer 201. For example, the hard mask layer 203 can better block oxygen atoms, and the pad oxide layer 201 can relatively allow oxygen atoms to diffuse. The blocking ability of the etch stop layer 202 to oxygen atoms is higher than the blocking ability of the pad oxide layer 201 and lower than the blocking ability of the hard mask layer 203. Therefore, in the subsequent thermal oxidation process for forming a local oxide, oxygen atoms can diffuse downward and relatively controllably into the substrate 200 through the etch stop layer 202, and the blocking ability of the etch stop layer 202 to oxygen atoms is related to its thickness. The thicker the thickness, the stronger the blocking ability.
[0040] Please continue to refer to Figure 3In step S2, a photoresist (not shown) is first coated on the hard mask layer 203, and the photoresist is subjected to photolithography (including exposure and development processes) to define the region where the local oxide is to be formed in the photoresist; then, the hard mask layer 203 is dry-etched using the photoresist after photolithography as a mask to open the hard mask layer 203 in the region where the local oxide is to be formed; then, the photoresist is removed, and the hard mask layer 203 is used as a mask, and HF acid, SPM (H2S The etch stop layer 202 and the pad oxide layer 201 are etched by a wet etching process using any suitable etching solution such as NH4OH, H2O2, and a mixture of H2O) or SC1 (a mixture of NH4OH, H2O2, and H2O) until the top surface of the substrate 200 is exposed, thereby forming a first opening 204 that penetrates the hard mask layer 203, the etch stop layer 202, and the pad oxide layer 201 from top to bottom in sequence, and the area defined by the first opening 204 is the main area where a local oxide is to be formed.
[0041] It should be understood that the size of the first opening 204 needs to be smaller than the size of the local oxide that is expected to be formed in the end, so that after undergoing thermal oxidation in step S5, the size of the local oxide that is actually formed in the end can reach the size of the local oxide that is expected to be formed, that is, the difference between the size of the local oxide that is actually formed in the end and the size of the local oxide that is expected to be formed does not exceed the range of device manufacturing requirements.
[0042] Please refer to Figure 4 In step S3, a photoresist layer is first coated on the hard mask layer 203 and the first opening 204, and the photoresist layer fills the first opening 204 and has a flat top surface; then the photoresist layer is subjected to photolithography (including a series of processes such as exposure and development) to form a patterned mask layer 300. The patterned mask layer 300 masks the area of the first opening 204 and forms a plurality of second openings in the area outside the first opening 204, and the line widths of the second openings on each side of the first opening 204 gradually decrease in a direction away from the first opening 204, so that when a local oxide is subsequently formed by thermal oxidation, the amount of oxygen passing through the second openings in a direction away from the first opening 204 is reduced, thereby controlling the bird's beak structure of the formed local oxide to be as short as possible.
[0043] It should be understood that the distribution of the second openings outside the first opening 204 is preferably symmetrical, so that the morphology of the local oxide formed subsequently is a symmetrical structure. Moreover, the size of each second opening is smaller than the first opening 204, wherein the number, shape, position, line width, spacing and other parameters of the second openings outside the first opening 204 depend on the requirements of the local oxide to be formed, and further depend on the difference between the corresponding parameters of the first opening and the local oxide to be formed. And the line width of each second opening and the spacing between adjacent second openings can enable the oxide layer formed in the substrate at the adjacent second openings to be connected as a whole when the local oxide is formed by subsequent thermal oxidation. The outermost second opening 205c can limit the terminal position and thickness of the bird's beak of the local oxide that is finally formed subsequently, and the distribution of the outermost second opening 205c can limit the edge position and shape of the local oxide that is finally formed.
[0044] In this embodiment, each second opening is formed as an annular opening surrounding the outer side of the first opening 204, and these second openings can be arranged in concentric rings to surround the first opening 204. In other embodiments of the present invention, when the first opening 204 is a strip-shaped opening, a plurality of strip-shaped second openings can also be symmetrically arranged only on opposite sides of the first opening 204, and these second openings are arranged parallel to the first opening 204 and sandwich the first opening in the middle.
[0045] Optionally, on each side of the first opening 204 , the interval between the second openings gradually decreases in a direction away from the first opening 204 .
[0046] Optionally, on each side of the first opening 204 , along a direction approaching the first opening 204 (ie, a direction opposite to a direction away from the first opening 204 ), the line width of any second opening is the same as the interval between the second opening and its adjacent second opening.
[0047] As an example, three second openings 205a, 205b, and 205c are formed on each side of the first opening 204 along the direction away from the first opening 204, and along the direction away from the first opening 204, the line width W3 of the second opening 205a, the line width W2 of the second opening 205b, and the line width W1 of the second opening 205c decrease successively, and along the direction away from the first opening 204, the interval D2 between the second opening 205a and the second opening 205b, and the interval D1 between the second opening 205b and the second opening 205c also decrease successively. Along the direction close to the first opening 204, the line width W1 of the second opening 205c is the same as the interval D1 between it and the second opening 205b, the line width W2 of the second opening 205b is the same as the interval D2 between it and the second opening 205a, and the line width W3 of the second opening 205a is the same as the interval D3 between it and the first opening 204, that is, W1=D1, W2=D2, W3=D3. In this way, the size of the openings including the first opening and the second opening is related to their blocking ability and the size of the OX formed in the substrate corresponding to these openings. At the same time, the size of the intervals between these openings also affects whether the OX under the two adjacent openings can be more easily contacted to form As a whole, it is set that starting from the first opening 204 and extending outward, each interval is sequentially the same size as the adjacent second opening, which can ensure that the substrate between two adjacent second openings and between the first opening and the second opening can eventually form a silicon dioxide layer that is connected as a whole more easily, which is further beneficial for ensuring the blocking effect while forming a more uniform extension structure on both sides of the oxide layer formed in the substrate below the first opening in the subsequent step S5, and is also beneficial for achieving the preset size of the first opening 204 being smaller than the size of the local oxide layer actually required, and finally forming a local oxide layer with good structural quality on the left and right sides in step S5, while making the bird's beak structure on the edge as small and controllable as possible.
[0048] In addition, it should be understood that, in this embodiment, the patterned mask layer 300 is a photoresist layer, but the technical solution of the present invention is not limited thereto. In other embodiments of the present invention, the patterned mask layer 300 may also include an amorphous carbon layer, a bottom anti-reflection layer, a top anti-reflection layer, etc. In addition, in other embodiments of the present invention, the patterned mask layer 300 may be a patterned dielectric layer formed by dielectric material deposition, photoresist coating, photolithography, and stripping processes.
[0049] Please refer to Figure 5In step S4, the hard mask layer 203 at each second opening is etched using the patterned mask layer 300 as a mask and the etch stop layer 202 as an etch stop layer. The etching can be stopped on the top surface of the etch stop layer 203 or at a corresponding depth of the etch stop layer 203, thereby deepening each second opening to a desired depth. The deepened second openings penetrate the hard mask layer 203 and the bottom does not expose the pad oxide layer 201. This step is to transfer the second openings in the patterned mask layer 300 to the hard mask layer 203. At this time, the top surface of the pad oxide layer 201 is not exposed at the bottom of each deepened second opening, and all the second openings outside the first opening 204 are equivalent to forming a comb-shaped opening. The hard mask layer 203 and the etch stop layer 202 between adjacent second openings serve as spacers (also called "spacers") between adjacent second openings, and the hard mask layer 203 and the etch stop layer 202 between the innermost second opening and the first opening 204 serve as spacers between the innermost second opening and the first opening.
[0050] The pad oxide layer 201 and the remaining etch stop layer 202 at each second opening can play a desired role in limiting the vertical diffusion of oxygen at the second opening when a local oxide is formed by thermal oxidation in the subsequent step S5 .
[0051] Optionally, the hard mask layer 203 at each second opening is etched using the patterned mask layer 300 as a mask to deepen each second opening to a desired depth. The thickness of the etching stop layer 202 remaining at the bottom of each second opening after deepening is
[0052] Optionally, on each side of the first opening 204 , the line width of the innermost second opening 205 a is 120 nm to 500 nm, and the line width of the outermost second opening 205 c is 80 nm to 200 nm.
[0053] Optionally, on each side of the first opening 204 , an interval between adjacent second openings is 80 nm to 200 nm.
[0054] It should be understood that in other embodiments of the present invention, the formation of the etch stop layer 202 may be omitted in step S1. In this case, in step S4, the hard mask layer 203 at each second opening is etched using the patterned mask layer 300 as a mask. When each second opening is deepened to a desired depth, the etching stops at the corresponding depth of the hard mask layer 203. The top surface of the pad oxide layer 201 is not exposed at the bottom of each deepened second opening. Because the blocking ability of the hard mask layer 203 to oxygen atoms is higher than that of the above-mentioned etch stop layer 202, in the absence of the etch stop layer 202, the thickness of the hard mask layer 203 remaining at the bottom of each deepened second opening is less than the thickness of the etch stop layer 202 remaining at the bottom of the deepened second opening in the above-mentioned solution, for example, less than
[0055] Optionally, in order to prevent the longitudinal dimension of the oxide layer formed at each second opening from being too large and the length of the oxide layer formed at the outermost second opening (e.g., 205c) extending outward laterally from being too long, before performing the subsequent thermal oxidation of step S5 and after forming the patterned mask layer 300 having the second opening, or before performing the subsequent thermal oxidation of step S5 and after etching the hard mask layer 203 at each second opening with the patterned mask layer 300 as a mask to deepen each second opening to a desired depth, the patterned mask layer is used as a mask to inject any suitable ions for suppressing the oxidation rate of the substrate into the substrate 200 below each second opening, so as to further reduce the oxidation rate of the substrate at the second opening in step S5, increase the oxidation rate difference between the substrate at the first opening and the substrate at the second opening, so that the edge of the local oxide layer finally formed extends to both sides as small as possible, so that the bird's beak shrinks faster. The ions for suppressing the oxidation rate of the substrate include, for example, nitrogen ions.
[0056] Please refer to Figure 5 In step S5, first, any suitable removal process is selected according to the material properties of the patterned mask layer 300 to remove the patterned mask layer 300 and re-expose the surface of the substrate 200 at the first opening 204. For example, when the patterned mask layer 300 is a photoresist, any suitable dry stripping or wet stripping process can be used to remove the patterned mask layer 300. Next, using any suitable thermal oxidation process such as furnace thermal oxidation, the surface layer of the substrate exposed at the first opening 204 directly reacts with oxygen and generates an oxide layer in situ, and since oxygen can also diffuse longitudinally from each second opening to the substrate below the bottom of the second opening, a corresponding oxide layer can also be formed in the substrate below the bottom of the second opening, and finally the oxide layers formed at the bottom of each second opening are connected in sequence and finally connected to the oxide layer formed at the first opening to form a local oxide 206.
[0057] During the thermal oxidation process in this step, firstly, since the size of the second opening is much smaller than that of the first opening and there is an oxygen barrier at the second opening, the substrate oxidation rate at the second opening is much smaller than that at the first opening, so the thickness of the oxide layer formed at the second opening is relatively thinner than that formed at the first opening. Secondly, in the lateral direction, since the line width and spacing of the second openings on each side of the first opening 204 gradually decrease in the direction away from the first opening 204, the amount of oxygen passing through the second openings can be reduced in the direction away from the first opening 204, and the oxide layers formed at the bottom of the second openings can be connected in sequence, and the bird's beak shrinks faster, so that the bird's beak structure of the local oxide 206 formed at the end of the thermal oxidation is smaller in the lateral direction, and the arrangement of the spacing size of the comb-like structure can be adjusted to achieve more precise control of the bird's beak morphology. Furthermore, the oxide layer formed under each second opening is equivalent to forming a multi-layer barrier layer, which can prevent the oxygen diffused laterally from the first opening 204 from continuing to diffuse laterally outward. Therefore, by precisely controlling the setting of the second openings, the lateral size of the oxide layer formed outside each side of the first opening 204 can be precisely controlled, and then the bird's beak size of the local oxide 206 can be precisely controlled, so that the bird's beak structure of the local oxide 206 formed at the end of thermal oxidation is as small and thin as possible in the lateral direction.
[0058] Optionally, in order to further accelerate the formation of local oxide and avoid the problem that the oxide layer formed at the second opening is still too large and too thick due to the long thermal oxidation time, any suitable ions for increasing the oxidation rate of the substrate 200 can be injected into the substrate 200 at the first opening 204 at any step node before performing thermal oxidation on the substrate 200 exposed by the first opening 204 in step S5, thereby further increasing the oxidation rate difference between the substrate at the first opening and the substrate at the second opening in step S5, so that the bird's beak shrinks faster. For example, after forming the first opening in step S2 and before performing step S3, ions for increasing the oxidation rate of the substrate 200 can be injected into the substrate 200 at the first opening 204 using the hard mask layer 203 as a mask; for example, after removing the patterned mask layer in step S5 and before performing thermal oxidation, ions for increasing the oxidation rate of the substrate 200 can be injected into the substrate 200 at the first opening 204 using the hard mask layer 203 as a mask. As an example, the ions used to increase the oxidation rate of the substrate 200 include at least one of oxygen ions, amorphization ions, and halogen ions. Among them, the implantation of oxygen ions can increase the oxygen content in the substrate 200, thereby increasing the oxidation rate of the substrate at the subsequent first opening 204 during oxidation; the amorphization ions include, for example, silicon ions, germanium ions, or argon ions, etc. The implantation of amorphization ions can form the single crystal silicon in the substrate 200 into amorphous silicon, thereby increasing the oxidation rate of the substrate at the subsequent first opening 204 during oxidation; the halogen ions include, for example, at least one of chloride ions (Cl), fluorine ions (F), and bromide ions (Br), and the implantation of halogen ions can act as a catalyst and has the effect of weakening the Si-O bond energy. Therefore, when the local oxide 206 is formed by thermal oxidation at the first opening 204, the SO bond energy of SiO2 of the formed local oxide 206 is weaker, making it easier for oxygen to diffuse into, thereby increasing the oxidation rate of the substrate during oxidation.
[0059] It should be understood that after forming the local oxide 206 , any suitable subsequent processes may be continued.
[0060] In one embodiment of the present invention, after forming the local oxide 206, the manufacturing method further includes: removing the hard mask layer 203, the etch stop layer 202 and the pad oxide layer 201 by any suitable process such as a wet etching process or a dry etching process. As an example, when the parameters such as the outer edge position of the first opening 204 and the position of the outermost second opening 205c are reasonably set, the local oxide 206 can be wet-etched at the same time as the pad oxide layer 201 is removed by the wet etching process to reduce the top surface height of the local oxide 206, and at the same time, the oxide layer under at least part of the second opening including the outermost second opening 205c is removed to reduce or remove the bird's beak of the local oxide 206. In this case, the thickness of the pad oxide layer 201 and the setting of the second opening 205c also determine the time of the wet etching, so the process of removing the bird's beak structure by the wet etching is equivalent to also taking the position parameters of the first opening and the outermost second opening as a reference, so that the process of removing the bird's beak structure is relatively more controllable and reliable.
[0061] As an example, any suitable etching solution such as HF acid, SPM (a mixture of H2SO4, H2O2, and H2O) or SC1 (a mixture of NH4OH, H2O2, and H2O) can be selected to wet-etch and remove the pad oxide layer 201, and at the same time, wet-etch the local oxide 206 to reduce the top surface height of the local oxide 206, and at the same time remove at least a portion of the oxide layer below the second opening including the outermost second opening 205c.
[0062] Optionally, after removing the hard mask layer 203 , the etch stop layer 202 and the pad oxide layer 201 , active devices such as transistors are manufactured based on the substrate 200 outside the local oxide 206 .
[0063] In another embodiment of the present invention, after forming the local oxide 206, the manufacturing method etches the bird's beak of the local oxide 206 (which may be only the area near the position of the second opening 205c, or the area from the position of the second opening 205c to the position of any second opening 205a on the inside) according to the outer edge position of the first opening 204 and the position of the outermost second opening 205c (or the position of each second opening) in some subsequent processes of etching the oxide, so as to remove the oxide layer under at least part of the second opening including the outermost second opening 205c, and reduce or remove the bird's beak of the local oxide 206. Obviously, the bird's beak structure removal process will be relatively more controllable and reliable because the position parameters of the first opening and the outermost second opening are used as references.
[0064] It should be understood that when it is necessary to ultimately manufacture a local oxide having a lateral dimension substantially the same as that of the prior art (i.e., the local oxide desired to be formed), the opening dimension of the first opening 204 formed in step S1 needs to be smaller than the lateral dimension of the local oxide desired to be formed, and the setting of the second openings on both sides of the first opening needs to take into account the difference between the lateral dimensions of the first opening and the local oxide desired to be formed, and the oxide layer formed in the substrate below the comb-shaped second openings in step S5 is also used as part of the local oxide actually formed, and is connected to the local oxide formed below the first opening, so that the local oxide actually formed finally obtains the same lateral dimension as the local oxide of the prior art.
[0065] In summary, the method for manufacturing a semiconductor device of the present invention, after etching the hard mask layer to form a first opening exposing a local area of the substrate to be oxidized, uses a patterned mask layer to mask the first opening, and forms a plurality of second openings in the area of the patterned mask layer located outside the first opening, so that when the hard mask layer is etched with the patterned mask layer as a mask, the second opening is transferred to the hard mask layer, and the line width of the second opening is gradually reduced in a direction away from the first opening, and when the patterned mask layer is removed and the substrate at the first opening is thermally oxidized, a small portion of oxygen diffuses downward from the second opening into the substrate to form an oxide layer, and the oxide layer formed at the first opening and the oxide layer formed at each second opening outside the first opening are The layers are connected as one to form a local oxide. On the one hand, the oxide layer formed at each second opening is finally connected to the oxide layer formed at the first opening, which can ensure that the lateral length of the formed local oxide meets the device manufacturing requirements. On the other hand, since the line width of the second opening on each side of the first opening gradually decreases in the direction away from the first opening, the amount of oxygen passing through the second opening can be reduced in the direction away from the first opening, and the oxide layer formed under each second opening can be used as a multi-layer barrier layer to prevent the oxygen diffused laterally from the first opening from continuing to diffuse outward, thereby accurately controlling the lateral size of the oxide layer formed outside each side of the first opening, and then accurately controlling the size of the bird's beak of the local oxide to make its bird's beak as small and thin as possible. In addition, after forming the local oxide, the oxide layer under at least part of the second opening including the outermost second opening can be etched and removed according to the outer edge position of the first opening and the position of the outermost second opening, thereby reducing or removing the bird's beak structure of the local oxide. Obviously, the bird's beak structure removal process will be relatively more controllable and reliable because of the position parameters of the first opening and the outermost second opening as a reference.
[0066] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.
Claims
1. A method for manufacturing a semiconductor device, characterized in that: The following steps are involved: providing a substrate, and forming a pad oxide layer and a hard mask layer on the substrate; etching the hard mask layer and the pad oxide layer to form a first opening exposing a local area of the substrate; forming a patterned mask layer, wherein the patterned mask layer masks the first opening and forms a plurality of second openings in a region outside the first opening, wherein the line width of the second openings gradually decreases in a direction away from the first opening; Using the patterned mask layer as a mask, etching the hard mask layer at the bottom of each second opening to deepen each second opening to a desired depth, wherein the bottom of each deepened second opening does not expose the pad oxide layer; The patterned mask layer is removed, and the substrate exposed by the first opening and the substrate under the second opening are thermally oxidized, so that the oxide layer formed at the first opening and the oxide layers formed at each second opening outside the first opening are connected together to form a local oxide.
2. The manufacturing method according to claim 1, characterized in that After forming the pad oxide layer on the substrate and before forming the hard mask layer, an etch stop layer is also formed on the pad oxide layer; when etching the hard mask layer at the bottom of each second opening using the patterned mask layer as a mask, the etching stops at the top surface of the etch stop layer or at a corresponding depth.
3. The manufacturing method according to claim 2, characterized in that: After forming the pad oxide layer on the substrate and before forming the hard mask layer, the thickness of the etch stop layer formed on the pad oxide layer is Alternatively, after deepening each of the second openings to a desired depth, the thickness of the etching stop layer remaining at the bottom of the second opening is 4. The manufacturing method according to claim 2, characterized in that: When etching the hard mask layer and the pad oxide layer to form the first opening, the hard mask layer is firstly dry-etched, and then the etch stop layer and the pad oxide layer are wet-etched until the top surface of the substrate is exposed.
5. The manufacturing method according to claim 1, characterized in that: At any step node after forming the patterned mask layer and before thermally oxidizing the substrate exposed by the first opening and the substrate below the second opening, ions for suppressing the oxidation rate of the substrate are implanted into the substrate below the second opening using the patterned mask layer as a mask; And / or, at any step node before thermally oxidizing the substrate exposed by the first opening, ions for increasing the oxidation rate of the substrate are implanted into the substrate at the first opening.
6. The manufacturing method according to claim 5, characterized in that: The ions for suppressing the substrate oxidation rate include nitrogen ions, and / or the ions for increasing the substrate oxidation rate include at least one of oxygen ions, amorphization ions and halogen ions.
7. The manufacturing method according to any one of claims 1 to 6, characterized in that: On each side of the first opening, the interval between the second openings gradually decreases along the direction away from the first opening; and / or, on each side of the first opening, along the direction close to the first opening, the line width of any second opening is the same as the interval between any second opening and its adjacent second opening.
8. The manufacturing method according to any one of claims 1 to 6, characterized in that On each side of the first opening, the line width of the innermost second opening is 120nm-500nm, and the line width of the outermost second opening is 80nm-200nm; and / or, the interval between adjacent second openings is 80nm-200nm.
9. The manufacturing method according to claim 1, characterized in that: The size of the first opening is smaller than the size of a desired local oxide. After thermal oxidation is performed on the substrate exposed by the first opening and the substrate under the second opening, the size of the actually formed local oxide reaches the size of the desired local oxide.
10. The manufacturing method according to claim 1, characterized in that: After forming the local oxide, the method further includes: etching and removing the oxide layer below at least a portion of the second opening including the outermost second opening according to the outer edge position of the first opening and the position of the outermost second opening, so as to reduce or remove the bird's beak structure of the local oxide.