Semiconductor structure and manufacturing method thereof
By performing ion implantation and etching on the mask layer to form trenches with different cross-sections and depths, the problem of complex optical waveguide structure fabrication in silicon photonics chip manufacturing is solved, achieving cost reduction and process simplification.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SIEN (QINGDAO) INTEGRATED CIRCUITS CO LTD
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-12
AI Technical Summary
In the current silicon photonics chip fabrication process, the multiple photomask and etching processes of the optical waveguide structure lead to complex process steps and high costs.
By performing ion implantation and etching on the mask layer to form trenches with different cross-sections and depths, the number of photolithography steps is reduced, and optical waveguides of various sizes can be formed in a single photolithography process.
The process steps were simplified, the number of photomasks used was reduced, and costs were lowered.
Smart Images
Figure CN122018078A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor integrated circuit technology, and in particular to a semiconductor structure and its fabrication method. Background Technology
[0002] In the fabrication of silicon photonic chips, in order to meet the signal input and output requirements of various devices, it is necessary to fabricate optical waveguides (WG) of various sizes, with different sizes and depths.
[0003] Because the structural parameters of various optical waveguides differ significantly, especially the critical dimensions and etching depths, existing processes typically rely on multiple independent photomasks, employing multiple photolithography and etching steps to fabricate different waveguide structures. This multi-photomask, multi-etching method is complex and costly. Summary of the Invention
[0004] The purpose of this application is to provide a semiconductor structure and a method for fabricating the same, which can reduce the number of process steps, the number of required photomasks, and the cost.
[0005] To address the aforementioned technical problems, according to the first aspect of this application, a method for fabricating a semiconductor structure is provided, comprising the following steps:
[0006] A substrate is provided, on which a sacrificial layer and a mask layer are sequentially formed;
[0007] The mask layer is etched to form two opening patterns that expose the sacrificial layer, wherein the cross-sectional size of the first opening pattern is larger than that of the second opening pattern;
[0008] Ion implantation is performed using the mask layer as a mask. The angle of ion implantation is adjusted so that ions are implanted into the sacrificial layer at the bottom of the first opening pattern to form a sacrificial treatment layer, while ions cannot be implanted into the sacrificial layer at the bottom of the second opening pattern.
[0009] Using the mask layer as a mask, a first etching is performed. During the etching, the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1 to remove the sacrificial treatment layer at the bottom of the first opening pattern, forming an initial trench at the bottom of the first opening pattern; and,
[0010] Using the mask layer as a mask, a second etching is performed to remove a portion of the substrate at the bottom of the first opening pattern and the bottom of the second opening pattern. A first trench is formed at the bottom of the first opening pattern, and a second trench is formed at the bottom of the second opening pattern. The cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench.
[0011] Optionally, the substrate includes a support substrate, a buried oxide layer, and a material layer stacked sequentially, wherein the first trench and the second trench are formed within the material layer.
[0012] Optionally, in the first etching, a portion of the mask layer of the sidewall thickness of the first opening pattern and the second opening pattern is also removed while the sacrificial treatment layer is being removed.
[0013] Optionally, the cross-sectional dimension of the first opening pattern is smaller than the cross-sectional dimension of the first trench, and the cross-sectional dimension of the second opening pattern is smaller than the cross-sectional dimension of the second trench.
[0014] Optionally, the material of the sacrificial layer includes silicon, the ion implanted includes oxygen ions, and the material of the sacrificial treatment layer includes silicon dioxide; or / and, the material of the mask layer includes silicon nitride.
[0015] Optionally, the density of oxygen atoms required to form a silicon dioxide layer of thickness d is: (2×ρ_SiO2×N_A / M_SiO2)×d, where ρ_SiO2 is the density of silicon dioxide, N_A is Avogadro's constant, and M_SiO2 is the molar mass of silicon dioxide.
[0016] Optionally, before forming the sacrificial layer on the substrate, the method further includes forming a buffer layer on the substrate, wherein the sacrificial layer is formed on the buffer layer.
[0017] Optionally, after forming the first trench and the second trench, the method further includes: etching the substrate to form a third trench within the substrate; the cross-sectional dimension of the third trench is smaller than the cross-sectional dimension of the first trench, and the cross-sectional dimension of the third trench is larger than the cross-sectional dimension of the second trench; and the depth of the third trench is smaller than the depth of the first trench, and the depth of the third trench is larger than the depth of the second trench.
[0018] Optionally, methods for etching the mask layer to form two opening patterns that expose the sacrificial layer include:
[0019] A photoresist layer is formed on the mask layer;
[0020] The photoresist layer is exposed and developed to form a patterned photoresist layer, and the patterned photoresist layer exposes the first opening pattern region and the second opening pattern region of the mask layer.
[0021] Using the patterned photoresist layer as a mask, the mask layer is etched until the sacrificial layer is exposed, forming the first opening pattern and the second opening pattern; and,
[0022] Remove the patterned photoresist layer.
[0023] To address the aforementioned technical problems, according to a second aspect of this application, a semiconductor structure is also provided, fabricated using the semiconductor structure fabrication method described above, wherein the semiconductor structure comprises:
[0024] Substrate;
[0025] A sacrificial layer is located on the substrate;
[0026] A mask layer is located on the sacrificial layer; and,
[0027] A first trench and a second trench extend through the mask layer and the sacrificial layer into the substrate, wherein the cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench.
[0028] In the semiconductor structure and fabrication method provided in this application, a sacrificial treatment layer is formed at the bottom of the first opening pattern by ion implantation, while the bottom of the second opening pattern remains a sacrificial layer as ion implantation cannot be performed. Then, a first etching is performed, in which the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1, thereby removing the sacrificial treatment layer at the bottom of the first opening pattern and forming an initial trench at the bottom of the first opening pattern. The sacrificial layer at the bottom of the second opening pattern is hardly etched. A second etching is then performed. Since the initial trench has already been formed at the bottom of the first opening pattern, the depth of the first trench formed at the bottom of the first opening pattern is greater than the depth of the second trench formed at the bottom of the second opening pattern. This allows for the formation of two trenches with different cross-sectional dimensions and depths in the same photolithography process, reducing process steps, saving on the number of photomasks used, and lowering costs. Attached Figure Description
[0029] Figures 1 to 6 This is a schematic diagram of the steps involved in the fabrication of semiconductor structures in related technologies.
[0030] Figure 7 This is a schematic flowchart of a method for fabricating a semiconductor structure according to an embodiment of this application.
[0031] Figures 8 to 13 This is a schematic diagram of the steps in a method for fabricating a semiconductor structure according to an embodiment of this application.
[0032] Explanation of reference numerals in the attached figures:
[0033] Figure 1 and Figure 6In the middle: 10-substrate; 11-supporting substrate; 12-buried oxide layer; 13-material layer; 20-buffer layer; 21-oxide layer; 22-nitride layer; 31-first patterned photoresist layer; 32-second patterned photoresist layer; 33-third patterned photoresist layer; 41-first trench; 42-second trench; 43-third trench.
[0034] Figures 8 to 13 In the middle: 100-substrate; 101-supporting substrate; 102-buried oxide layer; 103-material layer; 210-buffer layer; 220-sacrificial layer; 230-mask layer; 240-sacrificial treatment layer; 310-first patterned photoresist layer; 320-second patterned photoresist layer; 410-first opening pattern; 420-second opening pattern; 430-third opening pattern; 500-initial trench; 510-first trench; 520-second trench; 530-third trench. Detailed Implementation
[0035] Figures 1 to 6 This is a schematic diagram illustrating the steps involved in fabricating a semiconductor structure in related technologies. Please refer to the following first. Figure 1 As shown, a substrate 10 is provided, on which a buffer layer 20 is formed. In one embodiment, the substrate 10 includes a support substrate 11, a buried oxide layer 12, and a material layer 13 stacked sequentially, and the buffer layer 20 includes an oxide layer 21 and a nitride layer 22 stacked sequentially. Next, a first patterned photoresist layer 31 is formed on the buffer layer 20, exposing the region containing the first trench on the buffer layer 20. Then, please refer to... Figure 1 and Figure 2 As shown, using the first patterned photoresist layer 31 as a mask, the buffer layer 20 and the substrate 10 (e.g., material layer 13) are etched sequentially to form a first trench 41 in the substrate 10, and the first patterned photoresist layer 31 is removed.
[0036] Then please refer to Figure 3 As shown, a second patterned photoresist layer 32 is formed on the buffer layer 20. The second patterned photoresist layer 32 fills the first trench 41 and exposes the area where the second trench is located on the buffer layer 20. Please refer to [the document for further details]. Figure 3 and Figure 4 As shown, using the second patterned photoresist layer 32 as a mask, the buffer layer 20 and the substrate 10 (e.g., material layer 13) are etched sequentially to form a second trench 42 in the substrate 10, and the second patterned photoresist layer 32 is removed.
[0037] Next, please refer to Figure 5As shown, a third patterned photoresist layer 33 is formed on the buffer layer 20. This third patterned photoresist layer 33 fills the first trench 41 and the second trench 42, exposing the area where the third trench on the buffer layer 20 is located. Please refer to [the next section / reference]. Figure 5 and Figure 6 As shown, using the third patterned photoresist layer 33 as a mask, the buffer layer 20 and the substrate 10 (e.g., material layer 13) are etched sequentially to form a third trench 43 in the substrate 10, and the third patterned photoresist layer 33 is removed.
[0038] Please refer to Figure 6 As shown, a first trench 41, a second trench 42 and a third trench 43 are formed in the substrate 10, wherein the cross-sectional dimensions and depths increase sequentially from the first trench 41, the second trench 42 to the third trench 43.
[0039] In this embodiment, three trenches with different cross-sectional dimensions and depths are formed, requiring the formation of three patterned photoresist layers. This involves three exposure processes and three etching processes, making the process complex and costly.
[0040] To address the aforementioned problems, this application provides a semiconductor structure and its fabrication method. A sacrificial treatment layer is formed at the bottom of a first opening pattern by ion implantation, while the bottom of a second opening pattern remains a sacrificial layer as ion implantation is not possible. A first etching process is then performed, in which the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1, thereby removing the sacrificial treatment layer at the bottom of the first opening pattern and forming an initial trench at the bottom of the first opening pattern. The sacrificial layer at the bottom of the second opening pattern is hardly etched. A second etching process is then performed. Since the initial trench has already been formed at the bottom of the first opening pattern, the depth of the first trench at the bottom of the first opening pattern is greater than the depth of the second trench at the bottom of the second opening pattern. This allows for the formation of two trenches with different cross-sectional dimensions and depths within the same photolithography process, reducing process steps, saving on the number of photomasks used, and lowering costs.
[0041] Specifically, this application provides a method for fabricating a semiconductor structure, comprising: providing a substrate, and sequentially forming a sacrificial layer and a mask layer on the substrate; etching the mask layer to form two opening patterns exposing the sacrificial layer, wherein the cross-sectional size of the first opening pattern is larger than the cross-sectional size of the second opening pattern; performing ion implantation using the mask layer as a mask, adjusting the ion implantation angle so that ions are implanted into the sacrificial layer at the bottom of the first opening pattern to form a sacrificial treatment layer, while ions cannot be implanted into the sacrificial layer at the bottom of the second opening pattern; performing a first etching using the mask layer as a mask, wherein the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1 to remove the sacrificial treatment layer at the bottom of the first opening pattern, forming an initial trench at the bottom of the first opening pattern; and performing a second etching using the mask layer as a mask to remove a portion of the substrate at the bottom of the first and second opening patterns, forming a first trench at the bottom of the first opening pattern and a second trench at the bottom of the second opening pattern, wherein the cross-sectional size of the first trench is larger than the cross-sectional size of the second trench, and the depth of the first trench is greater than the depth of the second trench.
[0042] Accordingly, this application also provides a semiconductor structure fabricated using the semiconductor structure fabrication method described above. The semiconductor structure includes: a substrate; a sacrificial layer located on the substrate; a mask layer located on the sacrificial layer; a first trench and a second trench extending through the mask layer and the sacrificial layer into the substrate, wherein the cross-sectional dimension of the first trench is larger than the cross-sectional dimension of the second trench, and the depth of the first trench is greater than the depth of the second trench.
[0043] To make the objectives, advantages, and features of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, used only to facilitate and clarify the illustration of the embodiments of this application. Furthermore, the structures shown in the drawings are often part of the actual structures. In particular, different figures may emphasize different aspects and sometimes use different scales.
[0044] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature, unless otherwise expressly indicated.
[0045] Figure 7 This is a schematic flowchart illustrating a method for fabricating a semiconductor structure according to an embodiment of this application. Please refer to... Figure 7 As shown, the method for fabricating a semiconductor structure provided in this application includes the following steps:
[0046] S1: Provide a substrate, on which a sacrificial layer and a mask layer are sequentially formed;
[0047] S2: The mask layer is etched to form two opening patterns that expose the sacrificial layer, wherein the cross-sectional size of the first opening pattern is larger than that of the second opening pattern;
[0048] S3: Ion implantation is performed using the mask layer as a mask. The angle of ion implantation is adjusted so that ions are implanted into the sacrificial layer at the bottom of the first opening pattern to form a sacrificial treatment layer, while ions cannot be implanted into the sacrificial layer at the bottom of the second opening pattern.
[0049] S4: Perform the first etching using the mask layer as a mask. During the etching, the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1, so as to remove the sacrificial treatment layer at the bottom of the first opening pattern and form an initial trench at the bottom of the first opening pattern.
[0050] S5: Using the mask layer as a mask, a second etching is performed to remove a portion of the substrate at the bottom of the first opening pattern and the bottom of the second opening pattern. A first trench is formed at the bottom of the first opening pattern, and a second trench is formed at the bottom of the second opening pattern. The cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench.
[0051] Figures 8 to 13This is a schematic diagram of the steps involved in fabricating a semiconductor structure according to an embodiment of this application. Next, we will combine... Figure 7 , Figures 8 to 13 A method for fabricating a semiconductor structure according to an embodiment of this application will be described in detail.
[0052] In step S1, please refer to Figure 8 As shown, a substrate 100 is provided, on which a sacrificial layer 220 and a mask layer 230 are sequentially formed.
[0053] The substrate 100 can be made of silicon, germanium, silicon germanide, silicon carbide, silicon-on-insulator (SOI), germanium-on-insulator (GOI), or other materials such as gallium arsenide, gallium nitride, or indium gallium nitride, etc., which are III-V compounds. In one embodiment, the substrate 100 includes a support substrate 101, a buried oxide layer 102 on the upper surface of the support substrate 101, and a material layer 103 on the upper surface of the buried oxide layer 102. The support substrate 101 can be any suitable support material, such as silicon, ceramic, or quartz. The material layer 103 can be an optical waveguide material layer, such as a silicon layer or a silicon nitride layer.
[0054] First, a sacrificial layer 220 is formed on the substrate 100, covering the upper surface of the substrate 100. The sacrificial layer 220 serves the purpose of subsequently undergoing ion implantation to form a sacrificial treatment layer. This sacrificial treatment layer has a relatively high etch selectivity with the sacrificial layer 220, allowing for the removal of the sacrificial treatment layer with minimal etching of the sacrificial layer 220. Consequently, initial trenches are formed only at the locations of the sacrificial treatment layer during the same etching process. Therefore, the material of the sacrificial layer 220 can be any material that exhibits a relatively high etch selectivity after ion treatment compared to before ion treatment. In this embodiment, the material of the sacrificial layer 220 includes, but is not limited to, silicon. The sacrificial layer 220 can be formed using any suitable process, such as low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, or ultra-high vacuum chemical vapor deposition.
[0055] Next, a mask layer 230 is formed on the sacrificial layer 220, covering the upper surface of the sacrificial layer 220. The mask layer 230 acts as a mask during subsequent etching. The mask layer 230 can be any suitable material for masking; in this embodiment, the material of the mask layer 230 includes, but is not limited to, silicon nitride. The mask layer 230 can be formed using any suitable process known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition, or atomic layer deposition.
[0056] In one embodiment of this application, before forming the sacrificial layer 220 on the substrate 100, a buffer layer 210 is first formed on the substrate 100. The buffer layer 210 covers the upper surface of the substrate 100, specifically the upper surface of the material layer 103, and the sacrificial layer 220 covers the upper surface of the buffer layer 210. The material of the buffer layer 210 includes, but is not limited to, silicon dioxide. The buffer layer 210 can be formed using any suitable process known to those skilled in the art, such as thermal oxidation, chemical vapor deposition, physical vapor deposition, or atomic layer deposition.
[0057] In step S2, please continue to refer to Figure 8 As shown, the mask layer 230 is etched to form two opening patterns that expose the sacrificial layer 220. The cross-sectional size of the first opening pattern 410 is larger than the cross-sectional size of the second opening pattern 420.
[0058] For example, firstly, a photoresist layer is formed on the mask layer 230. The photoresist layer is then exposed and developed to form a patterned photoresist layer (referred to here as the first patterned photoresist layer 310 to distinguish it from subsequent patterned photoresist layers). The first patterned photoresist layer 310 exposes a first opening pattern region (i.e., the region containing the first opening pattern) and a second opening pattern region (i.e., the region containing the second opening pattern) of the mask layer 230. Then, using the first patterned photoresist layer 310 as a mask, the mask layer 230 is etched until the sacrificial layer 220 is exposed, forming the first opening pattern 410 and the second opening pattern 420. Afterwards, the first patterned photoresist layer 310 is removed.
[0059] The cross-sectional dimension of the first opening pattern 410 is larger than that of the second opening pattern 420. Subsequently, a first trench is formed in the substrate at the bottom of the first opening pattern 410, and a second trench is formed in the substrate 100 at the bottom of the second opening pattern 420, such that the cross-sectional dimension of the first trench is larger than that of the second trench. Wherein, cross-sectional dimension refers to... Figure 8 The dimensions shown in the horizontal direction represent the cross-sectional dimensions of the opening pattern, which are the opening dimensions. In this embodiment, two second opening patterns 420 are formed. This application does not limit the number of the first opening pattern 410 and the second opening pattern 420.
[0060] In step S3, please refer to Figure 9As shown, ion implantation is performed using the mask layer 230 as a mask. The angle of ion implantation is adjusted so that ions are implanted into the sacrificial layer 220 at the bottom of the first opening pattern 410 to form a sacrificial treatment layer 240, while ions cannot be implanted into the sacrificial layer 220 at the bottom of the second opening pattern 420.
[0061] The cross-sectional dimension of the first opening pattern 410 is larger than that of the second opening pattern 420. Therefore, by adjusting the direction of ion implantation, ions can be implanted into the sacrificial layer 220 at the bottom of the first opening pattern 410. The implanted ions react with the sacrificial layer 220 to form a sacrificial treatment layer 240. However, ions cannot be implanted into the sacrificial layer 220 at the bottom of the second opening pattern 420, but are only implanted into the sidewall of the mask layer 230. Thus, the bottom of the second opening pattern 420 is still the sacrificial layer 220.
[0062] In one embodiment of this application, the ion implantation area can be adjusted by simultaneously adjusting the direction of ion implantation and the thickness of the mask layer 230, such that the bottom of the first opening pattern 410 is the sacrificial treatment layer 240, and the bottom of the second opening pattern 420 is the sacrificial layer 220. Of course, the thickness of the mask layer 230 must also meet the requirements for its function as a mask.
[0063] In one embodiment of this application, the material of the sacrificial layer 220 includes, but is not limited to, silicon; the ion implanted ions include, but are not limited to, oxygen ions; the material of the sacrificial treatment layer 240 includes, but is not limited to, silicon dioxide; and the material of the mask layer 230 includes, but is not limited to, silicon nitride.
[0064] In one embodiment, the sacrificial layer 220 is made of silicon, the ions implanted are oxygen ions, and the sacrificial treatment layer 240 is made of silicon dioxide, meaning that silicon is oxidized to silicon dioxide through ion implantation. The core principle of this step is to use a high-energy ion beam to directly implant oxygen atoms into the silicon, and then use high-temperature annealing to allow the oxygen atoms to react with the silicon to form silicon dioxide; that is, high-temperature annealing is performed after ion implantation.
[0065] The number of injected oxygen atoms needs to be sufficient to completely react with the silicon in the injected region to form continuous and dense silica. Insufficient dosage will result in discontinuous, porous, or silicon-rich silica (SiO₂). x (x < 2), the higher the dosage, the thicker the formed silica, and the closer it is to the ideal stoichiometric ratio (i.e., SiO₂). x(x=2). The injected dose is approximately equal to the number of oxygen atoms required to form the target silica. The oxygen atom density required to form silica of thickness d is: (2×ρ_SiO2×N_A / M_SiO2)×d, where ρ_SiO2 is the density of silica, N_A is Avogadro's constant, and M_SiO2 is the molar mass of silica. Calculations show that forming 100nm of silica requires approximately an oxygen atom density of 4.6×10⁻⁶. 17 atoms / cm 2 Therefore, the typical dose for ion implantation (the dose commonly used) is (1~2×10⁻⁶). 18 The thickness of the resulting silica is typically in the range of 100nm to 400nm, depending on the annealing conditions and the original dosage.
[0066] In step S4, please refer to Figure 9 and Figure 10 As shown, the first etching is performed using the mask layer 230 as a mask. During the etching, the etching selectivity ratio of the sacrificial treatment layer 240 to the sacrificial layer 220 is greater than 10:1, so as to remove the sacrificial treatment layer 240 at the bottom of the first opening pattern 410 and form an initial trench 500 at the bottom of the first opening pattern 410.
[0067] In this embodiment, a dry etching process is used for the first etching. During the first etching, the etching gas is selected such that the etching selectivity ratio of the sacrificial treatment layer 240 to the sacrificial layer 220 is greater than 10:1, that is, the etching rate of the sacrificial treatment layer 240 is much greater than the etching rate of the sacrificial layer 220. This removes the sacrificial treatment layer 240 at the bottom of the first opening pattern 410, but almost no etching is performed on the sacrificial layer 220 exposed in the second opening pattern 420, thus forming the initial trench 500 only at the bottom of the first opening pattern 410.
[0068] In one embodiment of this application, a mixture of gas rich in fluorocarbon compounds (e.g., C4F8, CHF3) and argon may be used, but it is not limited to this.
[0069] In one embodiment of this application, during ion implantation of the sacrificial layer 220, ion implantation also occurs within the upper surface of the mask layer 230 and within the mask layer 230 on the sidewalls of the first opening pattern 410 and the second opening pattern 420. For example, when the mask layer 230 is silicon nitride and oxygen ion implantation is performed, the mask layer 230 on the sidewalls of the opening pattern and the top of the mask layer 230 are both oxygen-rich silicon nitride layers. Therefore, during the etching process to remove the sacrificial treatment layer 240, the mask layer 230 will also be slightly etched, such as... Figure 10As shown, the mask layer 230 on the sidewalls of the first opening pattern 410 and the second opening pattern 420 is also partially removed (where the dashed line refers to the opening pattern before the first etching). The resulting initial trench 500 has a cross-sectional dimension larger than the first opening pattern 410 (the original cross-sectional dimension, the cross-sectional dimension of the first opening pattern 410 formed in step S2). Furthermore, the cross-sectional dimensions of the first and second trenches formed subsequently by etching using the mask layer 230 as a mask are also larger than the cross-sectional dimension of the opening pattern. Therefore, the cross-sectional dimension of the opening pattern can be determined based on the required trench cross-sectional dimension and the thickness of the mask layer lost during the first etching (the thickness lost in the direction perpendicular to the sidewall of the opening pattern). Additionally, since this etching also etches the upper surface of the mask layer 230, the thickness of the mask layer 230 needs to be appropriately increased to prevent it from becoming too thin and failing to function as a mask.
[0070] In step S5, please refer to Figure 10 and Figure 11 As shown, a second etching is performed using the mask layer 230 as a mask to remove a portion of the substrate 100 at the bottom of the first opening pattern 410 and the bottom of the second opening pattern 420. A first trench 510 is formed at the bottom of the first opening pattern 410, and a second trench 520 is formed at the bottom of the second opening pattern 420. The cross-sectional dimension of the first trench 510 is larger than that of the second trench 520, and the depth of the first trench 510 is greater than that of the second trench 520.
[0071] Please refer to Figure 10 As shown, the first opening pattern 410 has an initial trench 500 formed at its bottom. Therefore, during the second etching, the remaining sacrificial layer 220, buffer layer 210, and substrate 100 are etched at the bottom of the initial trench 500. Since the second opening pattern 420 does not have an initial trench, the sacrificial layer 220, buffer layer 210, and substrate 100 of all thicknesses at the bottom of the second opening pattern 420 are etched simultaneously. This results in the depth of the first trench 510 formed at the bottom of the first opening pattern 410 being greater than the depth of the second trench 520 formed at the bottom of the second opening pattern 420.
[0072] In the second etching, etching stops when the second trench 520 reaches the target depth. The depth of the first trench 510 is then adjusted by changing the depth of the initial trench 500 so that the sum of the initial trench 500's depth and the second etching depth reaches the target depth of the first trench 510. The depth of the initial trench 500 is determined by the thickness of the sacrificial layer 220 and the ion implantation depth. By appropriately adjusting the thickness of the sacrificial layer 220 and the ion implantation dose, both the first trench 510 and the second trench 520 reach the target depth. Of course, since the cross-sectional size of the first trench 510 is larger than that of the second trench 520, the effect of the loading effect on etching must also be considered during the etching process. At the end of the second etching, both the first trench 510 and the second trench 520 have reached the required target depth.
[0073] In this embodiment, the first trench 510 and the second trench 520 with different depths and cross-sectional dimensions are formed by one photolithography and two etching processes. Compared with the prior art which requires two photolithography processes, one photolithography process is saved, thereby reducing the number of photomasks used and reducing costs.
[0074] This application forms a sacrificial treatment layer 240 at the bottom of the first opening pattern 410 by ion implantation, while the bottom of the second opening pattern 420 remains a sacrificial layer 220 as ion implantation cannot be performed. A first etching is then performed, with an etching selectivity ratio of more than 10:1 between the sacrificial treatment layer 240 and the sacrificial layer 220. This removes the sacrificial treatment layer 240 at the bottom of the first opening pattern 410, forming an initial trench 500 at the bottom of the first opening pattern 410. The sacrificial layer 220 at the bottom of the second opening pattern 420 is barely etched. A second etching is then performed. Since the initial trench 500 has already been formed at the bottom of the first opening pattern 410, the depth of the first trench 510 at the bottom of the first opening pattern 410 is greater than the depth of the second trench 520 at the bottom of the second opening pattern 420. This allows for the formation of two trenches with different cross-sectional dimensions and depths within the same photolithography process, reducing process steps, saving on the number of photomasks used, and lowering costs.
[0075] In one embodiment of this application, after forming the first trench 510 and the second trench 520, the method further includes: etching the substrate 100 to form a third trench 530 within the substrate 100; the cross-sectional dimension of the third trench 530 is smaller than the cross-sectional dimension of the first trench 510, and the cross-sectional dimension of the third trench 530 is larger than the cross-sectional dimension of the second trench 520; and the depth of the third trench 530 is smaller than the depth of the first trench 510, and the depth of the third trench 530 is greater than the depth of the second trench 520.
[0076] For example, please refer to Figure 12 As shown, a photoresist layer is formed on the mask layer 230. The photoresist layer is exposed and developed to form a second patterned photoresist layer 320. The second patterned photoresist layer 320 fills the first trench 510 and the second trench 520, and exposes the third opening pattern region of the mask layer (i.e., the region where the third trench or the third opening pattern is located). Then, using the second patterned photoresist layer 320 as a mask, the mask layer 230 is etched until the sacrificial layer 220 is exposed to form the third opening pattern 430.
[0077] Then, please refer to Figure 12 and Figure 13 As shown, using the second patterned photoresist layer 320 as a mask, the sacrificial layer 220, the buffer layer 210, and the substrate 100 are etched to form a third trench 530, after which the second patterned photoresist layer 320 is removed. The cross-sectional dimension of the third trench 530 is smaller than that of the first trench 510, and the cross-sectional dimension of the third trench 530 is larger than that of the second trench 520; furthermore, the depth of the third trench 530 is less than that of the first trench 510, and the depth of the third trench 530 is greater than that of the second trench 520.
[0078] In this embodiment, when three trenches with different cross-sectional dimensions and depths need to be formed, a first trench 510 with the largest cross-sectional dimension and the largest depth and a second trench 520 with the smallest cross-sectional dimension and the smallest depth are first formed using a first photolithography and etching process. Then, a third trench 530 is formed using a second photolithography and etching process, but this is not limited to this. The difference in cross-sectional dimensions between the first trench 510 and the second trench 520 formed in the same photolithography process needs to be relatively large, so that during ion implantation, adjustments can be made to ensure that ion implantation only implants into the bottom of the first opening pattern 410 and not into the bottom of the second opening pattern 420. Two trenches formed in the same photolithography process can be selected according to the required cross-sectional dimensions of each trench. In addition, another trench (e.g., a fourth trench) can also be formed simultaneously when forming the third trench 530.
[0079] In one embodiment of this application, the first trench 510, the second trench 520 and the third trench 530 formed in the substrate 100 can be optical waveguides. That is, the method described above can be used to form three optical waveguides with different key dimensions and depths by using two photolithography processes and etching, thereby saving one photolithography process and one mask layer, thus reducing costs.
[0080] In one embodiment of this application, after forming the trench, the process may further include removing the mask layer 230, the sacrificial layer 220, and the buffer layer 210.
[0081] In the semiconductor structure fabrication method provided in this application, a substrate 100 is first provided, and a sacrificial layer 220 and a mask layer 230 are sequentially formed on the substrate 100. Then, the mask layer 230 is etched to form two opening patterns exposing the sacrificial layer 220. The cross-sectional size of the first opening pattern 410 is larger than that of the second opening pattern 420. Next, ion implantation is performed using the mask layer 230 as a mask. The ion implantation angle is adjusted so that ions are implanted into the sacrificial layer 230 at the bottom of the first opening pattern 410 to form a sacrificial treatment layer 240, while ions cannot be implanted into the sacrificial layer 220 at the bottom of the second opening pattern 420. Then, a first etching is performed using the mask layer 230 as a mask. During the etching process, the sacrificial layer 220... The etching selectivity ratio of the processing layer 240 to the sacrificial layer 220 is greater than 10:1 to remove the sacrificial processing layer 240 at the bottom of the first opening pattern 410, forming an initial trench 500 at the bottom of the first opening pattern 410. Then, a second etching is performed using the mask layer 230 as a mask to remove a portion of the substrate 100 at the bottom of the first opening pattern 410 and the bottom of the second opening pattern 420. A first trench 510 is formed at the bottom of the first opening pattern 410, and a second trench 520 is formed at the bottom of the second opening pattern 420. The cross-sectional dimension of the first trench 510 is larger than that of the second trench 520, and the depth of the first trench 510 is greater than that of the second trench 520. This application forms a sacrificial treatment layer 240 at the bottom of the first opening pattern 410 by ion implantation, while the bottom 420 of the second opening pattern remains a sacrificial layer 220 as ion implantation cannot be performed. A first etching is then performed, with an etching selectivity ratio of more than 10:1 between the sacrificial treatment layer 240 and the sacrificial layer 220. This removes the sacrificial treatment layer 240 at the bottom of the first opening pattern 410, forming an initial trench 500 at the bottom of the first opening pattern 410. The sacrificial layer 220 at the bottom of the second opening pattern 420 is barely etched. A second etching is then performed. Since the initial trench 500 has already been formed at the bottom of the first opening pattern 410, the depth of the first trench 510 at the bottom of the first opening pattern 410 is greater than the depth of the second trench 520 at the bottom of the second opening pattern 420. This allows for the formation of two trenches with different cross-sectional dimensions and depths within the same photolithography process, reducing process steps, saving on the number of photomasks used, and lowering costs.
[0082] Accordingly, this application also provides a semiconductor structure fabricated using the semiconductor structure fabrication method described above. Please refer to... Figure 13 As shown, the semiconductor structure provided in this application embodiment includes:
[0083] Substrate 100;
[0084] Sacrificial layer 220 is located on the substrate 100;
[0085] Mask layer 230 is located on the sacrificial layer 220;
[0086] A first trench 510 and a second trench 520 extend through the mask layer 230 and the sacrificial layer 220 and into the substrate 100, wherein the cross-sectional dimension of the first trench 510 is larger than the cross-sectional dimension of the second trench 520, and the depth of the first trench 510 is greater than the depth of the second trench 520.
[0087] In one embodiment of this application, the material of the sacrificial layer 220 includes, but is not limited to, silicon, and the material of the mask layer 230 includes, but is not limited to, silicon nitride.
[0088] In one embodiment of this application, the substrate 100 includes a support substrate 101, a buried oxide layer 102, and a material layer 103 stacked sequentially, and the first trench 510 and the second trench 520 are formed in the material layer 103.
[0089] In one embodiment of this application, a third trench 530 is further included. The third trench 530 penetrates the mask layer 230 and the sacrificial layer 220 and extends into the substrate 100. The cross-sectional dimension of the third trench 530 is smaller than that of the first trench 510, and the cross-sectional dimension of the third trench 530 is larger than that of the second trench 520. The depth of the third trench 530 is smaller than that of the first trench 510, and the depth of the third trench 530 is greater than that of the second trench 520.
[0090] In summary, the semiconductor structure and fabrication method provided in this application firstly provide a substrate, on which a sacrificial layer and a mask layer are sequentially formed. Then, the mask layer is etched to form two opening patterns exposing the sacrificial layer. The cross-sectional size of the first opening pattern is larger than that of the second opening pattern. Next, ion implantation is performed using the mask layer as a mask. The ion implantation angle is adjusted so that ions are implanted into the sacrificial layer at the bottom of the first opening pattern to form a sacrificial treatment layer, while ions cannot be implanted into the sacrificial layer at the bottom of the second opening pattern. Finally, a first etching is performed using the mask layer as a mask. In the etching process, the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1 to remove the sacrificial treatment layer at the bottom of the first opening pattern, forming an initial trench at the bottom of the first opening pattern. Then, a second etching is performed using the mask layer as a mask to remove a portion of the substrate at the bottom of the first opening pattern and the bottom of the second opening pattern, forming a first trench at the bottom of the first opening pattern and a second trench at the bottom of the second opening pattern. The cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench. This application forms a sacrificial layer at the bottom of a first opening pattern by ion implantation, while the bottom of a second opening pattern remains a sacrificial layer as ion implantation is not possible. A first etching process is then performed, with an etching selectivity ratio greater than 10:1 between the sacrificial layer and the first opening pattern. This removes the sacrificial layer at the bottom of the first opening pattern, forming an initial trench at the bottom of the first opening pattern. The sacrificial layer at the bottom of the second opening pattern is barely etched. A second etching process is then performed. Since the initial trench has already formed at the bottom of the first opening pattern, the depth of the first trench at the bottom of the first opening pattern is greater than the depth of the second trench at the bottom of the second opening pattern. This allows for the formation of two trenches with different cross-sectional dimensions and depths within the same photolithography process, reducing process steps, saving on the number of photomasks used, and lowering costs.
[0091] The above description is merely a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A method for fabricating a semiconductor structure, characterized in that, Includes the following steps: A substrate is provided, on which a sacrificial layer and a mask layer are sequentially formed; The mask layer is etched to form two opening patterns that expose the sacrificial layer, wherein the cross-sectional size of the first opening pattern is larger than that of the second opening pattern; Ion implantation is performed using the mask layer as a mask. The angle of ion implantation is adjusted so that ions are implanted into the sacrificial layer at the bottom of the first opening pattern to form a sacrificial treatment layer, while ions cannot be implanted into the sacrificial layer at the bottom of the second opening pattern. The first etching is performed using the mask layer as a mask. During the etching, the etching selectivity ratio of the sacrificial treatment layer to the sacrificial layer is greater than 10:1, so as to remove the sacrificial treatment layer at the bottom of the first opening pattern and form an initial trench at the bottom of the first opening pattern. as well as, Using the mask layer as a mask, a second etching is performed to remove a portion of the substrate at the bottom of the first opening pattern and the bottom of the second opening pattern. A first trench is formed at the bottom of the first opening pattern, and a second trench is formed at the bottom of the second opening pattern. The cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench.
2. The method for fabricating a semiconductor structure according to claim 1, characterized in that, The substrate includes a support substrate, a buried oxide layer, and a material layer stacked sequentially, and the first trench and the second trench are formed within the material layer.
3. The method for fabricating a semiconductor structure according to claim 1, characterized in that, In the first etching, the mask layer, which is a portion of the thickness of the sidewalls of the first and second opening patterns, is removed while the sacrificial treatment layer is being removed.
4. The method for fabricating a semiconductor structure according to claim 3, characterized in that, The cross-sectional dimension of the first opening pattern is smaller than the cross-sectional dimension of the first trench, and the cross-sectional dimension of the second opening pattern is smaller than the cross-sectional dimension of the second trench.
5. The method for fabricating a semiconductor structure according to claim 1, characterized in that, The material of the sacrificial layer includes silicon, the ion implanted ions include oxygen ions, the material of the sacrificial treatment layer includes silicon dioxide; and / or the material of the mask layer includes silicon nitride.
6. The method for fabricating a semiconductor structure according to claim 5, characterized in that, The density of oxygen atoms required to form a silicon dioxide layer of thickness d is: (2×ρ_SiO2×N_A / M_SiO2)×d, where ρ_SiO2 is the density of silicon dioxide, N_A is Avogadro's constant, and M_SiO2 is the molar mass of silicon dioxide.
7. The method for fabricating a semiconductor structure according to claim 1, characterized in that, Before forming the sacrificial layer on the substrate, the method further includes forming a buffer layer on the substrate, wherein the sacrificial layer is formed on the buffer layer.
8. The method for fabricating a semiconductor structure according to claim 1, characterized in that, After forming the first trench and the second trench, the method further includes: etching the substrate to form a third trench within the substrate; the cross-sectional dimension of the third trench is smaller than the cross-sectional dimension of the first trench, and the cross-sectional dimension of the third trench is larger than the cross-sectional dimension of the second trench; and the depth of the third trench is smaller than the depth of the first trench, and the depth of the third trench is larger than the depth of the second trench.
9. The method for fabricating a semiconductor structure according to claim 1, characterized in that, The method of etching the mask layer to form two opening patterns that expose the sacrificial layer includes: A photoresist layer is formed on the mask layer; The photoresist layer is exposed and developed to form a patterned photoresist layer, and the patterned photoresist layer exposes the first opening pattern region and the second opening pattern region of the mask layer. Using the patterned photoresist layer as a mask, the mask layer is etched until the sacrificial layer is exposed, forming the first opening pattern and the second opening pattern; and, Remove the patterned photoresist layer.
10. A semiconductor structure, characterized in that, The semiconductor structure is fabricated using the method described in any one of claims 1 to 9, wherein the semiconductor structure comprises: Substrate; A sacrificial layer is located on the substrate; A mask layer is located on the sacrificial layer; and, A first trench and a second trench extend through the mask layer and the sacrificial layer into the substrate, wherein the cross-sectional dimension of the first trench is larger than that of the second trench, and the depth of the first trench is greater than that of the second trench.