A method for manufacturing a semiconductor structure

Abstract

The application provides a preparation method of a semiconductor structure and applies to the technical field of semiconductors.In the etching process of a metal (aluminum) wire with a dielectric anti-reflective layer (DARC), a traditional method is to detect the light intensity change of two wavelengths of fluorine and aluminum plasma by an endpoint detection system (EPD) to determine the etching endpoint of the DARC and the aluminum metal.The application adopts a new detection wavelength, sets a reasonable EPD algorithm, and uses the light intensity change of one fixed wavelength to identify the etching endpoints of the two media of the dielectric anti-reflective layer and the metal layer, that is, the two traditional wavelength signals are converted into one wavelength signal, so that the loss caused by the high-frequency signal conversion of the interferometer is eliminated, the identification accuracy of the interferometer is increased, and the service life of the interferometer is ultimately improved.

Description

Technical Field

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

[0002] Semiconductor integrated circuit chip manufacturing processes utilize batch processing technology to form a large number of complex devices of various types on the same silicon substrate and interconnect them to achieve complete electronic functions. With the rapid development of very large-scale integrated circuits, the integration density of chips is becoming increasingly higher and the size of components is becoming smaller and smaller. The various effects caused by the high density and small size of devices have an increasingly prominent impact on the semiconductor manufacturing structure.

[0003] Taking photolithography as an example, as semiconductor technology enters the 45-nanometer and below node, the linewidth of semiconductor devices is getting smaller and smaller, and the control of critical dimensions is becoming more and more important, which places higher and higher demands on photolithography processes. In order to meet the requirements of photolithography, in addition to upgrading photolithography equipment, a dielectric anti-reflective coating (DARC) layer can be deposited on the surface of the metal layer on products with smaller linewidths to improve the dimensional accuracy of the photolithography process.

[0004] However, due to the relatively low etching selectivity of the dielectric antireflective coating (DARC), an endpoint detection system (EPD) is required during the etching process to identify two different signals, F (wavelength 703nm) and Al (wavelength 396nm), using an interferometer to determine the etching stop time of the dielectric antireflective coating (DARC) and the underlying metal layer Metal in the semiconductor structure. This inevitably leads to long-term, high-frequency signal switching between the interferometer, which in turn exacerbates the wear of the controller gears, affects the interferometer's recognition accuracy, and ultimately seriously affects the service life of the interferometer. Summary of the Invention

[0005] The purpose of this invention is to provide a method for manufacturing a semiconductor structure that, by finding a suitable wavelength for the etching product elements and setting a reasonable EPD algorithm, can simultaneously identify both the anti-reflective dielectric layer DARC and the metal layer Metal using a fixed wavelength. This converts two wavelength signals into one wavelength signal, thereby eliminating the losses caused by high-frequency signal conversion in the interferometer, increasing the interferometer's recognition accuracy, and ultimately greatly improving the service life of the interferometer.

[0006] To address the aforementioned technical problems, this invention provides a method for fabricating a semiconductor structure, comprising the following steps:

[0007] A semiconductor substrate is provided, on the surface of which a developing resist layer, a dielectric anti-reflection layer, a first metal bonding layer, a metal layer and a second metal bonding layer are formed sequentially from top to bottom.

[0008] The semiconductor substrate is subjected to a first etching process, and the change in light intensity at a pre-selected wavelength is detected by an endpoint detection system (EPD) to determine the etching stop time of the dielectric anti-reflection layer etched in the first etching process.

[0009] The semiconductor substrate is subjected to a second etching process, and the change in light intensity of the pre-selected wavelength is detected again using the endpoint detection system EPD to determine the etching stop time of the metal layer etched in the second etching process.

[0010] The semiconductor substrate is over-etched to remove the second metal bonding layer, thereby forming a discrete structure on the surface of the semiconductor substrate consisting of the dielectric anti-reflective layer, the first metal bonding layer, the metal layer, and the second metal bonding layer.

[0011] Furthermore, the range of the pre-selected wavelength of the detection signal set by the endpoint detection system EPD in the first etching process and / or the second etching process can be 256nm to 266nm, and preferably, the pre-selected wavelength of the detection signal is 261nm.

[0012] Furthermore, before the development resist layer, the dielectric antireflective layer, the first metal bonding layer, the metal layer, and the second metal bonding layer are sequentially formed on the surface of the semiconductor substrate, a natural oxide layer may also be formed on the surface of the semiconductor substrate.

[0013] Furthermore, while over-etching the semiconductor substrate to remove the second metal bonding layer, a portion of the natural oxide layer can also be removed simultaneously.

[0014] Furthermore, the material of the metal layer may include AlCu.

[0015] Furthermore, the dielectric antireflective layer can be a silicide layer, and the specific material of the silicide layer can include silicon oxide or silicon oxynitride.

[0016] Furthermore, the step of determining the etching stop time of the etching process using an endpoint detection system (EPD) may include:

[0017] The pre-selected wavelength of the detection signal of the endpoint detection system EPD is set to 261nm. During the first etching process or the second etching process, the interferometer of the endpoint detection system EPD is used to detect the change of the emission spectrum curve of the generated plasma in each etching step. The emission spectrum curve is analyzed according to the corresponding algorithm to determine the etching stop time of each etching process.

[0018] Furthermore, the wavelength of the detected product in the first etching process is close to that of silicon, and the wavelength of the detected product in the second etching process is close to that of aluminum chloride.

[0019] Furthermore, the step of determining the etching stop time for each etching process based on the emission spectrum curve of the product in each etching step may include:

[0020] In the first etching process, the first etching process is stopped when the interferometer detects that the generated elements contain aluminum chloride; and in the second etching process, the second etching process is stopped when the interferometer detects that the light intensity corresponding to the wavelength of the aluminum chloride substance in the generated elements decreases.

[0021] Furthermore, the step of determining the etching time of the etching process using an endpoint detection system (EPD) may include:

[0022] The pre-selected wavelength of the detection signal of the endpoint detection system EPD is set to 261nm, and during the first etching process or the second etching process, the etching stop time of each etching process is determined based on the change of the plasma emission spectrum curve of each etching process and the corresponding EPD algorithm.

[0023] Compared with the prior art, the technical solution of the present invention has at least one of the following beneficial effects:

[0024] In the semiconductor structure fabrication method proposed in this invention, a two-step etching process is used for the dielectric anti-reflection layer and the metal layer stacked on the semiconductor substrate. In each etching process, the endpoint detection system (EPD) is used. By using the signal wavelength and EPD algorithm designed in this invention, it is only necessary to detect one wavelength in real time during the etching process to determine the precise etching stop time of each etching process.

[0025] Therefore, the inventive point of this invention lies in the following: by adopting a new detection wavelength and setting a reasonable EPD algorithm, the etching endpoints of the two media, the anti-reflection layer and the metal layer, can be identified by detecting the change in light intensity of a fixed wavelength. In other words, the two traditional wavelength signals are converted into one wavelength signal, thereby eliminating the loss caused by high-frequency signal conversion in the interferometer, increasing the recognition accuracy of the interferometer, and ultimately achieving the goal of improving the service life of the interferometer. Attached Figure Description

[0026] Figure 1 A graph showing the error judgment of etching signal for a dielectric antireflective coating (DARC) layer, plotted using existing EPD algorithms to capture data.

[0027] Figure 2A graph showing the error judgment of etching signals for a metal layer with AlCu as the metal material, plotted using the existing EPD algorithm to capture data;

[0028] Figure 3 A graph of the actual etching signal of the dielectric antireflective coating (DARC) plotted using the existing EPD algorithm to capture data;

[0029] Figure 4 A graph showing the actual etching signal of an AlCu metal layer plotted using existing EPD algorithms to capture data.

[0030] Figure 5 This is a schematic flowchart of a method for fabricating a semiconductor structure according to an embodiment of the present invention;

[0031] Figure 6 The actual etching signal curve of the dielectric antireflective coating (DARC) was plotted using the improved EPD algorithm of this invention;

[0032] Figure 7 The expected etching signal curve of the metal layer with AlCu metal material is used to utilize the improved EPD algorithm of this invention.

[0033] Figure 8 This refers to the configuration information corresponding to the improved EPD algorithm of this invention. Detailed Implementation

[0034] As described in the background section, in order to meet the requirements of photolithography, in addition to upgrading photolithography equipment, a dielectric antireflective coating (DARC) can be deposited on the surface of the metal layer on products with small linewidths to improve the dimensional accuracy of the photolithography process.

[0035] However, due to the relatively low etching selectivity of the dielectric antireflective coating (DARC), an endpoint detection system (EPD) is required during the etching process to identify two different signals, F (wavelength 703nm) and Al (wavelength 396nm), using an interferometer to determine the etching stop time of the dielectric antireflective coating (DARC) and the underlying metal layer Metal in the semiconductor structure, respectively. This will inevitably cause the interferometer to undergo long-term high-frequency wavelength signal switching, which will intensify the wear of the gears of the interferometer drive motor, affect the recognition accuracy of the interferometer, and ultimately seriously affect the service life of the interferometer.

[0036] For details, please refer to [link / reference]. Figures 1-2 ,in, Figure 1 A misjudgment curve of the etching signal of the dielectric antireflective coating (DARC) was plotted using the existing EPD algorithm to capture data. Figure 2This is a graph showing the misjudgment of etching signals for an AlCu metal layer, plotted using existing EPD algorithms to capture data. Figure 3 A graph showing the actual etching signal of the dielectric antireflective coating (DARC) plotted using existing EPD algorithms to capture data. Figure 4 This is a graph showing the actual etching signal of an AlCu metal layer, plotted using existing EPD algorithms to capture data. Figure 1 and Figure 3 , Figure 2 and Figure 4 The comparison shows that when the interferometer identifies two different signals F (wavelength 703nm) and Al (wavelength 396nm) to determine the etching stop time of the dielectric antireflective coating (DARC) and the underlying metal layer Metal in the semiconductor structure, it will make a misjudgment, which will result in the inability to accurately determine the etching stop time of the dielectric antireflective coating (DARC) and the AlCu metal layer respectively.

[0037] Based on this, the researchers of this invention propose that, in the existing technology for etching aluminum wires with a dielectric anti-reflective layer (DARC), the etching endpoints of DARC and aluminum are determined by detecting the intensity changes of two wavelengths of fluorine and aluminum plasma using an endpoint detection system (EPD). The invention proposes that it is possible to identify the etching endpoints of both the DARC and the underlying metal layer using only one wavelength, thereby eliminating the need for high-frequency signal conversion by an interferometer. This leads to the inventive concept of this invention: by finding suitable wavelengths for the etching product elements and setting a reasonable EPD algorithm, it is possible to simultaneously identify the etching endpoints of both the DARC and the metal layer using a single wavelength. This converts two wavelength signals into a single wavelength signal, eliminating the losses caused by high-frequency wavelength signal conversion in the interferometer, increasing the interferometer's recognition accuracy, and ultimately extending the interferometer's lifespan.

[0038] The light intensity of the detection signal corresponding to this wavelength is sufficient, and the two proposed media can clearly characterize different film layers.

[0039] Therefore, this invention provides a method for fabricating a semiconductor structure. By finding a suitable wavelength for the etching product elements and setting a reasonable EPD algorithm, it is possible to simultaneously identify the etching endpoints of both the dielectric antireflective layer (DARC) and the metal layer (Metal) using a single wavelength. This converts two wavelength signals into a single wavelength signal, thereby eliminating the losses caused by high-frequency signal conversion in the interferometer, increasing the interferometer's recognition accuracy, and ultimately improving the interferometer's lifespan.

[0040] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of a method for manufacturing a semiconductor structure according to the present invention. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may be implemented in other ways different from those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

[0041] As shown in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements. In detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0042] For example, you can refer to Figure 5 , Figure 5 This is a schematic flowchart of a method for fabricating a semiconductor structure according to an embodiment of the present invention, as shown below. Figure 5 As shown, the preparation method provided by the present invention specifically includes the following steps:

[0043] Step S100: A semiconductor substrate is provided, and a developing resist layer, a dielectric anti-reflective layer, a first metal adhesive layer, a metal layer, and a second metal adhesive layer are sequentially formed from top to bottom on the surface of the semiconductor substrate.

[0044] In this embodiment, a semiconductor substrate is first required. The semiconductor substrate can be any suitable substrate known in the art, such as at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors. It also includes multilayer structures composed of these semiconductors, or silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeOI), and germanium-on-insulator (GeOI). Alternatively, it can be a double-sided polished wafer (DSP), or a ceramic substrate such as alumina, a quartz substrate, or a glass substrate. For example, in this embodiment, the semiconductor substrate is a silicon wafer.

[0045] Subsequently, a developing resist layer, a dielectric antireflective layer, a first metal bonding layer, a metal layer, and a second metal bonding layer are sequentially formed from top to bottom on the surface of the semiconductor substrate using chemical vapor deposition or physical vapor deposition. The dielectric antireflective layer is a silicide layer, specifically a silicon oxide, silicon oxynitride, or a bilayer of silicon oxide and silicon oxynitride. The first and / or second metal bonding layers, serving as the bonding layers for the metal layers, can be titanium, titanium nitride, or a bilayer of titanium and titanium nitride. Further, the material of the metal layer can be AlCu.

[0046] It is understood that, in the embodiments of the present invention, after a semiconductor substrate is provided and before the film layer is sequentially formed on the surface of the semiconductor substrate, the semiconductor substrate exposed to air will be oxidized by oxygen atoms in the air, thereby forming a natural oxide layer on the surface of the semiconductor substrate.

[0047] Step S200: Perform a first etching process on the semiconductor substrate, and use an endpoint detection system (EPD) to detect the change in light intensity at a pre-selected wavelength to determine the etching stop time of the dielectric anti-reflection layer etched in the first etching process.

[0048] In this embodiment, the pre-selected wavelength range of the detection signal set by the endpoint detection system EPD in the first etching process is 256nm to 266nm, specifically 256nm, 257nm, 258nm, 259nm, 260nm, 261nm, 262nm, 263nm, 264nm, 265nm, and 266nm. Preferably, in the embodiment provided by this invention, the pre-selected wavelength of the detection signal set by the endpoint detection system EPD in the first etching process is 261nm. The first etching process can be a dry etching process.

[0049] In this embodiment, after the multilayer stacked film is formed in step S100, a two-step etching process can be used to etch the dielectric antireflective layer and the metal layer respectively. First, a first-step etching process can be performed on the dielectric antireflective layer and the first metal bonding layer in the multilayer stacked film. During this first-step etching process, the interferometer of the endpoint detection system (EPD) can be used to detect the intensity change of the emission wavelength of the specific etching product formed in the first-step etching process in real time. Conversely, the etching process at this time can be determined, and the etching stop time of the first-step etching process can be determined by combining the EPD algorithm.

[0050] As an example, this embodiment of the invention provides a method for using an interferometer of an endpoint detection system (EPD) to detect the migration change of the emission wavelength in a specific product in each etching process, and designing a corresponding EPD algorithm based on the spectral curve change to determine the endpoint of each etching step, as follows: First, the pre-selected wavelength of the detection signal of the endpoint detection system (EPD) is set to 261nm. When the interferometer in the first etching process detects that the light intensity of the corresponding wavelength changes from decreasing to increasing, i.e., aluminum chloride is detected, the first etching process is stopped.

[0051] Among them, the endpoint detection system (EPD) utilizes the change in light intensity at a specific wavelength from the start to the end of etching, and obtains the most suitable endpoint of etching by setting an appropriate algorithm.

[0052] As another example, the EPD algorithm in the endpoint detection system EPD can be used to capture information from the spectral curve formed by the interferometer, and the etching stop time for each etching process can be determined based on the material changes represented by the peaks or troughs in the etching signal curve.

[0053] It should be noted that the overall inventive concept of the two examples above is, firstly, to improve the existing EPD algorithm, that is, to adjust the wavelength of the detection signal in the EPD algorithm, and then to analyze the spectral curve of the signal at that wavelength using a suitable EPD algorithm, such as... Figure 8 As shown, where, Figure 8This refers to the configuration information corresponding to the improved EPD algorithm of this invention. In this embodiment of the invention, the wavelength is specifically adjusted to 261nm. Then, in the first etching process, the interferometer monitors the spectral curve formed by the product of the etching reaction at a wavelength of 261nm, and the EPD algorithm is used to capture the inflection point of the spectral curve, such as... Figure 6 As shown, the EPD algorithm begins image capture during the first descent of the spectral curve and continues until the spectral curve changes from descent to rise, at which point it performs the final image capture and issues the first etching termination signal.

[0054] Figure 6 The actual etching signal curve of the dielectric antireflective coating (DARC) was plotted using the improved EPD algorithm of this invention.

[0055] according to Figure 6 It can be seen that the actual etching signal curve of the dielectric antireflective coating (DARC) plotted using the improved EPD algorithm of this invention specifically includes etching stage a of the dielectric antireflective coating, etching stage b of the first metal bonding layer, and etching stage c of the metal layer. Therefore, according to Figure 6 The trough transition at the junction of etching stage b of the first metal adhesive layer and etching stage c of the metal layer can determine the etching stop time of the first etching process.

[0056] In step S300, a second etching process is performed on the semiconductor substrate, and the change in light intensity of the pre-selected wavelength is detected again using the endpoint detection system EPD to determine the etching stop time of the metal layer etched in the second etching process.

[0057] In this embodiment, a second etching process can be performed on the metal layer using the same execution procedure as the first etching process. In this second etching process, when the interferometer detects that the spectral curve formed by the product at a wavelength of 261 nm begins to decrease, the second etching process is stopped. Figure 7 As shown, where, Figure 7 The image shows the expected etching signal curve for a metal layer made of AlCu, obtained using the improved EPD algorithm of this invention. Specifically, in the second etching step, the second metal bonding layer is used as an etching stop layer, and then the metal layer is etched in the second step.

[0058] Step S400: The semiconductor substrate is over-etched to remove the second metal adhesive layer, thereby forming a discrete structure on the surface of the semiconductor substrate consisting of the dielectric anti-reflective layer, the first metal adhesive layer, the metal layer, and the second metal adhesive layer.

[0059] In this embodiment, after the above two etching steps are stopped, the semiconductor substrate can be over-etched to remove the second metal bonding layer and form a discrete structure on the surface of the semiconductor substrate consisting of the dielectric anti-reflective layer, the first metal bonding layer, the metal layer and the second metal bonding layer.

[0060] Furthermore, since the natural oxide layer is also formed below the second metal adhesive layer, while the semiconductor substrate is over-etched in step S400 to remove the second metal adhesive layer, this step can also simultaneously remove a portion of the natural oxide layer.

[0061] In summary, the semiconductor structure fabrication method proposed in this invention employs a two-step etching process for the dielectric antireflective layer and the metal layer stacked on the semiconductor substrate. In each etching step, an endpoint detection system (EPD) is used. By utilizing the signal wavelength and EPD algorithm designed in this invention, the precise etching stop time for each etching step can be determined simply by detecting the spectral curve represented by the wavelength of the product in real time during the etching process.

[0062] Therefore, the inventive point of this invention lies in the following: by adopting a new detection wavelength and setting a reasonable EPD algorithm, the etching endpoints of the two media, the anti-reflection layer and the metal layer, can be identified by detecting the change in light intensity of a fixed wavelength. In other words, the two traditional wavelength signals are converted into one wavelength signal, thereby eliminating the loss caused by high-frequency signal conversion in the interferometer, increasing the recognition accuracy of the interferometer, and ultimately achieving the goal of improving the service life of the interferometer.

[0063] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the scope of protection of the present invention.

[0064] It should also be understood that, unless otherwise specified or indicated, the terms “first,” “second,” “third,” etc., in the specification are used only to distinguish the various components, elements, and steps in the specification, and not to indicate the logical or sequential relationships between the various components, elements, and steps.

[0065] Furthermore, it should be recognized that the terminology described herein is used only to describe particular embodiments and not to limit the scope of the invention. It must be noted that the singular forms “a” and “an” used herein and in the appended claims include plural bases unless the context clearly indicates otherwise. For example, a reference to “a step” or “an apparatus” means a reference to one or more steps or apparatuses, and may include secondary steps and secondary apparatuses. All conjunctions used should be understood in the broadest sense. Also, the word “or” should be understood to have the definition of logical “or” rather than logical “exclusive OR”, unless the context clearly indicates otherwise. Furthermore, implementation of the methods and / or devices in embodiments of the invention may include performing selected tasks manually, automatically, or in combination.

Claims

1. A method for fabricating a semiconductor structure, characterized in that, Includes the following steps: A semiconductor substrate is provided, on the surface of which a developing resist layer, a dielectric anti-reflection layer, a first metal bonding layer, a metal layer and a second metal bonding layer are formed sequentially from top to bottom. The semiconductor substrate is subjected to a first etching process, and the change in light intensity at a pre-selected wavelength is detected by an endpoint detection system (EPD) to determine the etching stop time of the dielectric anti-reflection layer etched in the first etching process. The semiconductor substrate is subjected to a second etching process, and the change in light intensity of the pre-selected wavelength is detected again using the endpoint detection system EPD to determine the etching stop time of the metal layer etched in the second etching process. The semiconductor substrate is over-etched to remove the second metal bonding layer, thereby forming a discrete structure on the surface of the semiconductor substrate consisting of the dielectric anti-reflective layer, the first metal bonding layer, the metal layer, and the second metal bonding layer.

2. The method for preparing the semiconductor structure according to claim 1, characterized in that, The pre-selected wavelength range of the detection signal set by the endpoint detection system EPD in the first etching process and / or the second etching process is 256nm to 266nm.

3. The method for preparing the semiconductor structure as described in claim 1, characterized in that, Before the development resist layer, dielectric antireflective layer, first metal bonding layer, metal layer and second metal bonding layer are sequentially formed on the surface of the semiconductor substrate, a natural oxide layer is also formed on the surface of the semiconductor substrate.

4. The method for preparing a semiconductor structure as described in claim 3, characterized in that, While the semiconductor substrate is being over-etched to remove the second metal bonding layer, a portion of the natural oxide layer is also being removed simultaneously.

5. The method for preparing a semiconductor structure as described in claim 1, characterized in that, The material of the metal layer includes AlCu.

6. The method for preparing a semiconductor structure as described in claim 1, characterized in that, The dielectric antireflective layer is a silicide layer, and the material of the silicide layer includes silicon oxide or silicon oxynitride.

7. The method for preparing a semiconductor structure as described in claim 2, characterized in that, The steps for determining the etching stop time of an etching process using an endpoint detection system (EPD) to detect a specific wavelength signal include: The pre-selected wavelength of the detection signal of the endpoint detection system EPD is set to 261nm. During the first or second etching process, the etching stop time of each etching process is determined by using the emission spectrum of the endpoint detection system EPD and the corresponding algorithm based on the changes in the plasma emission spectrum curve of each etching process.

8. The method for preparing a semiconductor structure as described in claim 7, characterized in that, The product detected in the first etching process is a silicon-containing compound, and the product detected in the second etching process is an aluminum chloride compound.

9. The method for preparing a semiconductor structure as described in claim 8, characterized in that, The step of determining the etching stop time for each etching process based on the change in the emission spectrum curve of the selected product in each etching process includes: In the first etching process, the first etching process is stopped when the interferometer detects an increase in the light intensity corresponding to aluminum chloride; and in the second etching process, the second etching process is stopped when the interferometer detects a decrease in the light intensity corresponding to the wavelength of the generated aluminum chloride.

10. The method for preparing a semiconductor structure as described in claim 2, characterized in that, The steps for determining the etching time of an etching process using an endpoint detection system (EPD) with controllable detection signal wavelength include: The pre-selected wavelength of the detection signal of the endpoint detection system EPD is set to 261nm. During the first etching process or the second etching process, the emission spectrum curve formed by the corresponding wavelength is detected by the endpoint detection system EPD. The spectrum curve is analyzed by the corresponding algorithm to determine the etching stop time of each etching process.

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