An etching method

Abstract

The application provides an etching method, and provides an etching structure, which comprises an insulating layer, a metal layer and a patterned photoresist layer arranged on the insulating layer in sequence; the photoresist layer is used as a mask, and the metal layer is etched by using an inert gas ion beam at a first etching angle to obtain an etching groove; a metal deposition layer is formed on the sidewall surface of the photoresist layer during the etching process; the photoresist layer and the metal deposition layer are etched by using a mixed gas ion beam at a second etching angle to remove the metal deposition layer; the mixed gas comprises inert gas and reactive gas, the reactive gas can react with the photoresist layer and can consume the photoresist layer, so that the aspect ratio of the etching groove is reduced, the etching of the metal deposition layer by the mixed gas ion beam is facilitated, the mixed gas is incident into the etching groove at the second etching angle, the second etching angle is greater than the first etching angle, the metal deposition layer can be completely removed, the damage to the insulating layer is reduced, and the yield of the metal electrode is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor process technology, and in particular to an etching method. Background Technology

[0002] In the fabrication of metal electrodes, the selection of metal layer materials must consider the performance requirements of the device, including resistivity, adhesion characteristics, thin film deposition conditions, and selectivity. Metals such as gold, silver, and platinum offer significant performance characteristics, including low resistivity, high chemical stability, high melting point, low surface work function, and good ohmic contact with other metals. Therefore, gold, silver, and platinum are widely used as metal layers in electrode fabrication.

[0003] Metal etching is generally divided into two types: wet etching and dry etching. As feature resolution gradually decreases, dry etching has attracted much attention due to its high transfer accuracy. Compared with wet etching, the most important advantage of dry etching in a plasma environment is that it can avoid lateral drilling and has a lower roughness, resulting in fewer pits in the metal layer.

[0004] In existing technologies, during the etching of metals in a plasma environment, redeposition problems can occur on the sidewalls. Ion beam etching (IBE) can be used to remove the residue on the sidewalls. However, in high aspect ratio structures, the incident angle of the ion beam is limited, making it difficult to fully utilize its advantages. It is impossible to completely remove the residue on the sidewalls, and it is easy to over-etch the underlying insulating layer, affecting the yield of the metal electrode. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide an etching method that can completely remove the residual metal deposit layer on the sidewalls with minimal damage to the insulating layer. The specific solution is as follows:

[0006] In a first aspect, this application provides an etching method, comprising:

[0007] A structure to be etched is provided, the structure to be etched includes an insulating layer, and a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer;

[0008] Using the photoresist layer as a mask, an inert gas ion beam is used to etch the metal layer at a first etching angle to obtain an etching trench; a metal deposition layer is formed on the sidewall surface of the photoresist layer during the etching process;

[0009] The photoresist layer and the metal deposition layer are etched using a mixed gas ion beam at a second etching angle to remove the metal deposition layer; the mixed gas includes an inert gas and a reactive gas; the second etching angle is greater than the first etching angle.

[0010] Optionally, the etching trench extends through the metal layer, and when the photoresist layer and the metal deposition layer are etched using a mixed gas ion beam at a second etching angle, the metal layer at the bottom of the etching trench is removed.

[0011] Optionally, the reactant gas is oxygen, nitric oxide, carbon monoxide, carbon dioxide, or a fluorine / chlorine-based gas.

[0012] Optionally, the flow rate of the inert gas in the mixed gas is greater than or equal to 0.5.

[0013] Optionally, the second etching angle ranges from 45° to 75°.

[0014] Optionally, the second etching angle ranges from 60° to 75°.

[0015] Optionally, the range of the first etching angle is 0 to 20°.

[0016] Optionally, the metal layer material is gold, silver, platinum, or copper.

[0017] Optionally, the inert gas flow rate in the mixed gas is 15-60 sccm, and the reactant gas flow rate in the mixed gas is 2-20 sccm.

[0018] Optionally, the beam current voltage of the inert gas ion beam and the mixed gas ion beam is 100V-600V; the particle acceleration voltage of the inert gas ion beam and the mixed gas ion beam is 50V-100V.

[0019] This application provides an etching method. First, a structure to be etched is provided, including an insulating layer, a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer. Next, using the photoresist layer as a mask, an inert gas ion beam is used to etch the metal layer at a first etching angle to obtain an etching trench. During the etching process, a metal deposition layer is formed on the sidewall surface of the photoresist layer, which seriously affects subsequent processes. Then, a mixed gas ion beam is used to etch the photoresist layer and the metal deposition layer at a second etching angle to remove the metal deposition layer. The mixed gas includes an inert gas and a reactive gas. The reactive gas can react with the photoresist layer and consume it, thereby reducing the aspect ratio of the etching trench, avoiding repeated metal deposition on the sidewalls, and facilitating the etching of the metal deposition layer by the mixed gas ion beam. The mixed gas is incident into the etching trench at a second etching angle, which is greater than the first etching angle. This allows for the complete removal of the metal deposition layer, reduces damage to the insulating layer, and improves the yield of the metal electrode. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the structure formed after gold etching is shown;

[0022] Figure 2 A schematic flowchart of an etching method provided in an embodiment of this application is shown;

[0023] Figure 3 , 4 Figure 5 shows a schematic diagram of a structure to be etched according to an embodiment of this application;

[0024] Figure 6 This illustration shows a structural diagram of a metal-deposited layer removed, according to an embodiment of this application.

[0025] Figure 7 This illustration shows a schematic diagram of the structure of a metal deposition layer modified with argon gas according to an embodiment of this application.

[0026] Figure 8 This illustration shows a schematic diagram of sample elemental analysis provided in an embodiment of this application. Detailed Implementation

[0027] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0029] As described in the background section, when etching metals in a plasma environment, such as in an inductively coupled plasma (ICP) system, metals can be etched. However, etching byproducts are prone to redeposit on the sidewalls of the masking photoresist, forming metal fences, and this phenomenon is difficult to completely eliminate by optimizing process parameters. Figure 1The diagram shows the structure formed after gold etching, including a silicon dioxide layer, a gold layer, and a photoresist layer arranged sequentially from bottom to top. It can be seen that after gold etching, a veil-like sidewall deposition is formed on the sidewall of the photoresist, which seriously affects subsequent processes and thus reduces the yield of metal electrodes.

[0030] The inventors discovered that post-processing cleaning can remove sidewall residues. IBE (In-Etching Beam) is a dry etching technology developed in the 1970s. It utilizes an ion source to bombard the target material with energetic ions, causing sputtering on the material surface to remove the material. This purely physical bombardment method allows it to etch any material. Thanks to its angled etching characteristics, IBE has a unique advantage in removing non-volatile metal sidewall deposits. However, in high aspect ratio structures, the ion beam incident angle is limited, making it difficult to fully utilize its advantages, resulting in incomplete removal of sidewall residues and a tendency to over-etch the underlying substrate. Furthermore, the high-energy ion bombardment of the photoresist causes it to deform, forming a hardened shell, which also affects subsequent photoresist removal.

[0031] Based on the above technical problems, this application provides an etching method. First, a structure to be etched is provided, including an insulating layer, a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer. Next, using the photoresist layer as a mask, an inert gas ion beam is used to etch the metal layer at a first etching angle to obtain an etching trench. During the etching process, a metal deposition layer forms on the sidewall surface of the photoresist layer, which severely affects subsequent processes. Then, a mixed gas ion beam is used to etch the photoresist layer and the metal deposition layer at a second etching angle to remove the metal deposition layer. The mixed gas includes an inert gas and a reactive gas. The reactive gas can react with the photoresist layer, consuming it and reducing the aspect ratio of the etching trench. This avoids repeated metal deposition on the sidewalls and facilitates the etching of the metal deposition layer by the mixed gas ion beam. The mixed gas is incident into the etching trench at a second etching angle greater than the first etching angle. This allows for complete removal of the metal deposition layer, reduces damage to the insulating layer, and improves the yield of the metal electrode.

[0032] For ease of understanding, the etching method provided in this application embodiment will be described in detail below with reference to the accompanying drawings.

[0033] refer to Figure 2 The diagram shown is a flowchart of an etching method provided in an embodiment of this application. The method may include the following steps.

[0034] S101 provides a structure to be etched, the structure to be etched includes an insulating layer, and a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer.

[0035] In this embodiment of the application, the structure to be etched is first provided, with reference to... Figure 3 As shown, the structure to be etched includes an insulating layer 100, a metal layer 110, and a patterned photoresist layer 120 arranged sequentially from bottom to top. The structure to be etched can be formed on a silicon substrate, or the insulating layer 100 can be used as the substrate. The insulating layer 100 can be made of silicon dioxide, and the metal layer 110 can be made of gold, silver, platinum, or copper.

[0036] S102, using the photoresist layer as a mask, an inert gas ion beam is used to etch the metal layer at the first etching angle to obtain an etching trench; a metal deposition layer is formed on the sidewall surface of the photoresist layer during the etching process.

[0037] In this embodiment, the structure to be etched can be transferred to a reactive ion beam etching machine. A first etching angle is formed between the surface normal of the structure and the incident ion beam. Then, an inert gas is introduced into the discharge chamber, and plasma etching is performed on the structure to be etched using a patterned photoresist layer 120 as a mask to open the metal layer 110 and obtain the etching trench 130. (Refer to...) Figure 4 As shown. During the etching process, since plasma etching forms the etching trench 130 through physical bombardment, it easily leads to the formation of a metal deposition layer 140 on the sidewall surface of the photoresist layer. The metal deposition layer 140 will seriously affect subsequent processes and the yield of the metal electrode. The inert gas can be argon or helium.

[0038] S103, using a mixed gas ion beam at a second etching angle to etch the photoresist layer and the metal deposition layer to remove the metal deposition layer; the mixed gas includes an inert gas and a reactive gas; the second etching angle is greater than the first etching angle.

[0039] In this embodiment, the structure to be etched can be etched again to remove the metal deposition layer 140, as shown in the reference. Figure 5 As shown, a mixed gas can be introduced into the discharge chamber. The mixed gas is a mixture of inert gas and reactive gas in a certain proportion, and then the sidewall of the etching trench 130 is modified by the mixed gas ion beam at the second etching angle.

[0040] Specifically, refer to Figure 6The diagram shown is a schematic representation of a structure with the metal deposition layer removed, provided in an embodiment of this application. Inert gas and reactive gas work together on the metal deposition layer. The inert gas physically bombards and modifies the sidewall contaminants, i.e., the metal deposition layer. The reactive gas, while assisting in modifying the metal deposition layer, reacts with the photoresist layer, acting as reactive ion etching. This accelerates the consumption of the photoresist layer, reduces the aspect ratio of the etching trench, and prevents repeated metal deposition on the sidewalls. Simultaneously, the defect of the metal deposition layer can be indirectly utilized as a protective layer for the photoresist during oxygen etching. The metal deposition layer ensures that the photoresist layer is not consumed too quickly during etching, ensuring that photoresist consumption and sidewall modification occur simultaneously. This allows for complete removal of the metal deposition layer with minimal damage to the bottom insulating layer. It also ensures minimal photoresist residue, avoiding the difficulty in removal caused by photoresist degradation. Wet photoresist removal leaves no thin film residue, improving the yield of the metal electrode.

[0041] refer to Figure 7 The diagram shown illustrates the structure of a metal deposition layer modified with argon gas according to an embodiment of this application. The inert gas ion beam incident angle is 55°, the ion energy is 400V, the particle acceleration bias voltage is 80V, the etching chamber pressure is 0.6mT, the inert gas flow rate is 24sccm, the inert gas is argon, and the etching time is 360s. It is evident that due to the aspect ratio of the etching trench, the ion beam modification angle is relatively small, resulting in a large amount of etching of the insulating layer. The silicon oxide insulating layer is etched through, and typical metal deposition still exists on the top of the metal layer, severely affecting device performance and yield. Compared to pure inert gas modification of the sidewalls, this application offers a wider etching angle, shorter modification time, and less damage to the bottom insulating layer, demonstrating significant potential in high aspect ratio metal electrode etching.

[0042] In this embodiment, the flow rate ratio of the inert gas in the mixed gas can be greater than or equal to 0.5, specifically determined by the metal material and the aspect ratio of the etching tank. The reactant gas can be oxygen, nitric oxide, carbon monoxide, carbon dioxide, or fluorine / chlorine-based gases.

[0043] In this embodiment of the application, the etching trench can partially penetrate the metal layer, such as... Figure 4 As shown, when etching the photoresist layer and the metal deposition layer using a mixed gas ion beam at the second etching angle, the metal layer at the bottom of the etching trench is removed simultaneously with the metal deposition layer. It is understood that the etching trench can also completely penetrate the metal layer; in this case, when etching the photoresist layer and the metal deposition layer using a mixed gas ion beam at the second etching angle, it is not necessary to remove the metal layer at the bottom of the etching trench.

[0044] In this embodiment, the etching angle can be selected based on the aspect ratio of the etching trench, and the range of the second etching angle can be 45° to 75°. More specifically, the range of the second etching angle is 60° to 75°, for example, 70°. The range of the first etching angle can be 0° to 20°, for example, 15°.

[0045] In this embodiment, the selection of the process gas flow rate depends on the uniformity of the sample to be etched. The inert gas flow rate in the mixed gas can be 15-60 sccm, and the reactant gas flow rate in the mixed gas can be 2-20 sccm. During the etching of the metal layer using an inert gas ion beam at a first etching angle, the inert gas flow rate can also be 15-60 sccm.

[0046] In this embodiment, the beam current voltage (BMV) during the process depends on the required etching rate and the characteristics of the etching material itself. The beam current voltage for inert gas ion beams and mixed gas ion beams can be 100V-600V. The particle acceleration bias voltage (ACV) is adjusted according to the set value of BMV, following the principle of keeping the ACV value as small as possible. The particle acceleration voltage for inert gas ion beams and mixed gas ion beams can be 50V-100V.

[0047] In the embodiments of this application, the etching method of this application can be used to prepare a blazed grating. The following process parameters can be set: the incident angle of the mixed gas ion beam is 75°, the particle acceleration bias voltage is 80V, the etching chamber pressure is 0.6mT, the mixed gas includes argon and oxygen, the ratio of argon to oxygen is 3:1, the total gas flow rate is 24sccm, and the etching time is 360s. Then, a blazed grating that meets the requirements can be prepared.

[0048] In this embodiment, after removing the metal deposition layer, the oxygen content on the metal sidewalls is higher than the oxygen content at the photoresist-masked areas. Specifically, after removing the metal deposition layer and the remaining photoresist layer, the oxygen content on the metal surface can be analyzed using an energy dispersive spectroscopy (EDS) instrument. (Reference) Figure 8 The diagram shown is a schematic diagram of elemental analysis of a sample provided in an embodiment of this application. Elemental analysis revealed the presence of oxygen around the modified metal layer, indicating that when oxygen participates in sidewall modification, oxides are generated and adhere to the metal layer. However, the top of the metal layer is protected by photoresist and does not react with oxygen, so no oxide generation was observed.

[0049] In the embodiments of this application, it can be understood that when the photoresist CD is greater than 1µm, the etching depth of the dielectric layer in the process path of this application is much lower than that of conventional modification processes.

[0050] This application provides an etching method. First, a structure to be etched is provided, including an insulating layer, a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer. Next, using the photoresist layer as a mask, an inert gas ion beam is used to etch the metal layer at a first etching angle to obtain an etching trench. During the etching process, a metal deposition layer is formed on the sidewall surface of the photoresist layer, which seriously affects subsequent processes. Then, a mixed gas ion beam is used to etch the photoresist layer and the metal deposition layer at a second etching angle to remove the metal deposition layer. The mixed gas includes an inert gas and a reactive gas. The reactive gas can react with the photoresist layer and consume it, thereby reducing the aspect ratio of the etching trench, avoiding repeated metal deposition on the sidewalls, and facilitating the etching of the metal deposition layer by the mixed gas ion beam. The mixed gas is incident into the etching trench at a second etching angle, which is greater than the first etching angle. This allows for the complete removal of the metal deposition layer, reduces damage to the insulating layer, and improves the yield of the metal electrode.

[0051] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the apparatus embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0052] The above description is merely a preferred embodiment of this application. Although this application has disclosed preferred embodiments above, it is not intended to limit this application. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this application using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of this application. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this application without departing from the content of the technical solutions of this application shall still fall within the protection scope of the technical solutions of this application.

Claims

1. An etching method, characterized in that, include: A structure to be etched is provided, the structure to be etched includes an insulating layer, and a metal layer and a patterned photoresist layer sequentially disposed on the insulating layer; Using the photoresist layer as a mask, the metal layer is etched at a first etching angle using an inert gas ion beam to obtain an etching trench; A metal deposition layer is formed on the sidewall surface of the photoresist layer during the etching process; The photoresist layer and the metal deposition layer are etched using a mixed gas ion beam at a second etching angle to remove the metal deposition layer. The mixed gas includes an inert gas and a reactive gas. The second etching angle is greater than the first etching angle. During the etching process, the inert gas and the reactive gas act together on the metal deposition layer. The inert gas modifies the metal deposition layer through physical bombardment, while the reactive gas, while assisting in modifying the metal deposition layer, reacts with the photoresist layer to perform reactive ion etching, accelerating the consumption of the photoresist layer, reducing the aspect ratio of the etching trench, and preventing repeated metal deposition on the sidewalls, thereby removing the metal deposition layer. The second etching angle ranges from 45° to 75°, and the first etching angle ranges from 0° to 20°.

2. The method according to claim 1, characterized in that, The etching trench extends through the metal layer, and when the photoresist layer and the metal deposition layer are etched using a mixed gas ion beam at a second etching angle, the metal layer at the bottom of the etching trench is removed.

3. The method according to claim 1, characterized in that, The reacting gas is oxygen, nitric oxide, carbon monoxide, carbon dioxide, or fluorine / chlorine-based gas.

4. The method according to claim 1, characterized in that, The flow rate of the inert gas in the mixed gas is greater than or equal to 0.5%.

5. The method according to claim 1, characterized in that, The second etching angle ranges from 60° to 75°.

6. The method according to any one of claims 1-5, characterized in that, The metal layer material is gold, silver, platinum, or copper.

7. The method according to any one of claims 1-5, characterized in that, The inert gas flow rate in the mixed gas is 15-60 sccm, and the reactant gas flow rate in the mixed gas is 2-20 sccm.

8. The method according to any one of claims 1-5, characterized in that, The beam current voltage of the inert gas ion beam and the mixed gas ion beam is 100V-600V; the particle acceleration voltage of the inert gas ion beam and the mixed gas ion beam is 50V-100V.

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