A method of cleaning a reaction chamber and a plasma etching apparatus

Abstract

The application discloses a kind of reaction cavity cleaning method and plasma etching equipment, after processing substrate in the reaction cavity, the residue in the reaction cavity is cleaned, comprising: the first mixed gas is introduced into the reaction cavity, the first mixed gas is dissociated into plasma, the first mixed gas includes Cl2 and O2, the volume ratio of Cl2 and O2 is greater than 1;The second mixed gas is introduced into the reaction cavity, the second mixed gas is dissociated into plasma, the second mixed gas includes Cl2 and O2, the volume ratio of Cl2 and O2 is less than 1.Compared with only introducing single gas, the removal efficiency of the mixed gas provided by the application to residue is high, and the stability of the reaction cavity environment can be guaranteed.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more specifically to a method for cleaning a reaction chamber and a plasma etching apparatus. Background Technology

[0002] After the semiconductor substrate has been processed within the reaction chamber, it is typically removed and the chamber is cleaned (wafer-less clean) to remove any residue left on the chamber walls or other components from the reaction process. This cleaning step usually involves introducing a cleaning gas into the reaction chamber, igniting plasma, and then using the plasma to remove residue. After the cleaning step is complete, the next step of substrate processing continues.

[0003] Existing cleaning processes are still insufficient to effectively remove non-volatile residues within the reaction chamber, affecting subsequent substrate processing steps. Therefore, a new reaction chamber cleaning method needs to be developed to thoroughly remove these residues. Summary of the Invention

[0004] The purpose of this invention is to provide a cleaning method that can thoroughly remove residues from the reaction chamber.

[0005] To achieve the above objectives, the present invention provides a method for cleaning a reaction chamber, comprising cleaning residues in the reaction chamber after processing a substrate therein, including:

[0006] A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is greater than 1.

[0007] A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is less than 1.

[0008] Optionally, the volume ratio of Cl2 to O2 in the first mixed gas ranges from 2:1 to 10:1.

[0009] Optionally, the volume ratio of Cl2 to O2 in the second mixed gas ranges from 1:10 to 1:2.

[0010] Optionally, the first mixed gas also includes Ar, and the volume ratio of Cl2 to Ar is in the range of 1:4 to 4:1.

[0011] Optionally, the second mixed gas also includes Ar, wherein the volume ratio of Ar to O2 is less than 1.

[0012] Optionally, the first mixed gas, after dissociating into plasma, is used at least to clean up metal residues in the reaction chamber.

[0013] Optionally, the metal residue contains at least one of Cr and Ti.

[0014] Optionally, the metal residue includes any one or more of CrCl2, CrCl3, Cr2O3, Cr, or TiF4.

[0015] Optionally, the second mixed gas, after dissociating into plasma, is used to clean at least one of the fluorocarbon residues and hydrocarbon residues in the reaction chamber.

[0016] Optionally, the cleaning time for the first mixed gas to dissociate into plasma is 10-60 s.

[0017] Optionally, the cleaning time for the second mixed gas to dissociate into plasma is 10-60 s.

[0018] Optionally, the cleaning time for the first mixed gas to dissociate into plasma is greater than the cleaning time for the second mixed gas to dissociate into plasma.

[0019] Optionally, the pressure within the reaction chamber where the first mixed gas dissociates into plasma is 5mT-50mT.

[0020] Optionally, the pressure within the reaction chamber where the second mixed gas dissociates into plasma is 10mT-100mT.

[0021] Optionally, the first mixed gas further includes BCl3, wherein the volume ratio of BCl3 to Cl2 is less than 0.1:1.

[0022] Optionally, the second mixed gas further includes BCl3, wherein the volume ratio of BCl3 to Cl2 is less than 0.1:1.

[0023] Optionally, the substrate comprises, from bottom to top, a substrate, a titanium dioxide layer, a chromium film layer, and a mask layer; processing the substrate in the reaction chamber includes the following steps:

[0024] An etching gas containing Cl2 and C is introduced. x H y F z Gas, wherein 0 < x ≤ 4, y ≥ 0, z ≥ 0, and y and z do not both take the value of 0;

[0025] Using the mask layer as a mask, the chromium film layer is etched, and then using the chromium film layer as a mask, the titanium dioxide layer is etched to form a titanium dioxide nanostructure on the substrate.

[0026] The present invention also provides a plasma etching apparatus, comprising:

[0027] reaction chamber;

[0028] The Cl2 gas source and the O2 gas source are connected to the reaction chamber through gas pipelines;

[0029] A radio frequency source is used to excite the gas in the reaction chamber into plasma; and,

[0030] The controller is configured to perform the following steps:

[0031] A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is greater than 1.

[0032] A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is less than 1.

[0033] The beneficial effects of this invention are as follows:

[0034] (1) After the substrate is processed, the substrate is removed and a mixture of Cl2 and O2 is introduced into the reaction chamber to clean the reaction chamber (wafer-less clean). Compared with only introducing a single gas, the mixed gas has a high removal efficiency for residues and can ensure the stability of the reaction chamber environment.

[0035] (2) Both the first mixed gas and the second mixed gas of the present invention contain at least Cl2 and O2. Cl2 is predominant in the first mixed gas and is used to clean metal residues in the reaction chamber. O2 is predominant in the second mixed gas and is used to clean fluorocarbon or fluorocarbon residues in the reaction chamber. Therefore, the method provided by the present invention can use the same type of gas to clean different types of residues in the reaction chamber by adjusting the gas flow rate.

[0036] (3) In view of the problem that BCl3 gas may corrode the reaction chamber, the present invention strictly controls the amount of BCl3 gas introduced, so as to give full play to the cleaning effect of BCl3 on non-volatile residues and reduce the negative impact of adding BCl3 on the anodic oxidation area in the reaction chamber.

[0037] (4) Under the process conditions of the present invention, the first mixed gas or the second mixed gas ion bombardment is weak and the corrosion of the reaction chamber is low. After cleaning, the inner wall of the reaction chamber still has better uniformity and does not affect the continued use of the reaction chamber.

[0038] (5) The reaction chamber cleaning method provided by the present invention can be used in microlens manufacturing or in chips using TiO2 as the gate sidewall (spacer) material. Attached Figure Description

[0039] Figure 1 This is a flowchart of the reaction chamber cleaning method according to an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the etching process in which the substrate is etched into a microlens according to the present invention.

[0041] Figure 3 This is a line graph showing the substrate etching rate according to an embodiment of the present invention.

[0042] Figure 4 This is a line graph showing the substrate etching rate as a comparative example.

[0043] Figure 5 A schematic diagram to verify the bombardment intensity under the process conditions in Examples 1-3.

[0044] In the figure, 100-substrate, 200-titanium dioxide layer, 201-titanium dioxide nanostructure, 300-chromium film layer, 301-chromium nanostructure, 400-mask layer, 401-mask nanostructure, 500-area to be etched. Detailed Implementation

[0045] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] This invention provides a method for cleaning a reaction chamber. After processing a substrate in the reaction chamber, the method cleans the residue inside the chamber by introducing a first mixed gas and a second mixed gas into the reaction chamber. This invention does not limit the order in which the first and second mixed gases are introduced. The steps for introducing the first mixed gas and the second mixed gas are described below.

[0048] (i) Introduce the first mixed gas into the reaction chamber.

[0049] A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 (chlorine) and O2 (oxygen), with a volume ratio of Cl2 to O2 greater than 1, meaning that Cl2 is dominant in the first mixed gas. Optionally, the volume ratio of Cl2 to O2 ranges from 2:1 to 10:1. The plasma from the first mixed gas is used at least to clean metal residues in the reaction chamber. The metal residues contain at least one of Cr (chromium) and Ti (titanium). Metal residues containing Cr include any one or more of CrCl2 (chromium dichloride), CrCl3 (chromium trichloride), Cr2O3 (chromium trioxide), and elemental Cr. Metal residues containing Ti include TiF4 (titanium tetrafluoride).

[0050] Breaking the chemical bonds of non-volatile metal residues to form volatile gases containing metal elements is key to removing them. After Cl2 dissociates from O2, the reaction chamber contains a large number of Cl* (chlorine radicals) and O* (oxygen radicals). The bombardment energy of Cl* and O* is high, which is conducive to the breaking of chemical bonds.

[0051] Cl2→2Cl*(1)

[0052] O2→2O*(2)

[0053] For Cr-containing metal residues such as CrCl2, CrCl3, or Cr2O3, it is necessary to break the Cr-Cl or Cr-O bonds. Cl* and O* react with Cr-containing metal residues (s) to generate gaseous CrO2Cl2 (g), achieving a removal effect.

[0054] CrCl2 or CrCl3: CrCl x (s)+2O*+(2-x)Cl*→CrO2Cl2(g)(3)

[0055] Cr2O3: Cr2O3(s)+O*+4Cl*→2CrO2Cl2(g)(4)

[0056] Cl* and O* can also react with elemental Cr: Cr(s) + 2O* + 2Cl* → CrO2Cl2(g) (5)

[0057] According to reaction formulas (3) and (4), the amount of Cl2 consumed is greater than that of O2, so in the first mixed gas, the amount of Cl2 is dominant.

[0058] For Ti-containing metal residues such as TiF4, it is necessary to break the Ti-F bonds. O* reacts with TiF4 to form solid TiO2; Cl* can further break the Ti-O bonds and react with TiO2 to form gaseous TiCl4, thus removing TiF4.

[0059] TiF4(s) + 2O* → TiO2(s) + 2F2(6)

[0060] TiO2(s) + 4Cl* → TiCl4(g) + O2 (7)

[0061] According to reaction equations (6) and (7), although both Cl2 and O2 participate in the reaction, O2 is not actually consumed in the process; only Cl2 is continuously consumed. The addition of O2 accelerates the scavenging of TiF4.

[0062] (ii) Introduce a second mixed gas into the reaction chamber.

[0063] A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas comprises Cl2 (chlorine) and O2 (oxygen), with a Cl2 to O2 volume ratio less than 1, meaning that O2 is dominant in the second mixed gas. Optionally, the Cl2 to O2 volume ratio ranges from 1:10 to 1:2. The plasma, after dissociation, is used to clean at least one of the fluorocarbon residues and hydrocarbon residues within the reaction chamber.

[0064] Boron trichloride (BCl3) is a gas with strong reducing properties. Adding BCl3 can significantly enhance the cleaning effect of the reaction chamber. However, BCl3 reacts with Al2O3, posing a potential risk of corrosion to the reaction chamber.

[0065] BCl3 + e → [BCl2] + +Cl*+2e (8)

[0066] [BCl2] + (g) + Al₂O₃(s) → Al(s) + O(s) + BO x Cl y (g)(9)

[0067] To fully utilize the cleaning effect of BCl3 on non-volatile residues while minimizing its negative impacts, this application strictly controls the amount of BCl3 added. In both the first and second mixed gases, the volume ratio of BCl3 to Cl2 is less than 0.1:1.

[0068] In some embodiments, the cleaning time for the first mixed gas to dissociate into plasma is 10-60 s. The cleaning time for the second mixed gas to dissociate into plasma is 10-60 s. The cleaning time for the first mixed gas to dissociate into plasma is greater than the cleaning time for the second mixed gas to dissociate into plasma.

[0069] In some embodiments, the pressure within the reaction chamber where the first mixed gas dissociates into plasma is 5 mT-50 mT. The pressure within the reaction chamber where the second mixed gas dissociates into plasma is 10 mT-100 mT. The first mixed gas is used to clean metal residues. Since metal compounds have high chemical bond energies, sufficiently high ion bombardment energy is required to break these bonds. Therefore, when the first mixed gas dissociates into plasma for cleaning, the gas pressure within the reaction chamber must be relatively low to enhance the ion bombardment capability.

[0070] In some embodiments, the first gas mixture further includes Ar, with a Cl2 to Ar volume ratio ranging from 1:4 to 4:1. The second gas mixture further includes Ar, with an Ar to O2 volume ratio of less than 1. Ar is used to increase the energy of the first or second gas mixture.

[0071] In some embodiments, processing the substrate within the reaction chamber involves etching the substrate into a microlens. For example... Figure 2 As shown, the substrate comprises, from bottom to top, a substrate 100, a titanium dioxide layer 200, a chromium film layer 300, and a mask layer 400. To form the titanium dioxide nanostructure 201, the surface of the mask layer 400 is patterned: the mask layer 400 includes multiple mask nanostructures 401, optionally, the mask nanostructures 401 are columnar. The gap between two adjacent mask nanostructures 401 serves as the etching region 500. Etching gas enters the mask layer 400 from the etching region 500, etching the portion of the chromium film layer 300 corresponding to the etching region 500 along the thickness direction of the mask layer 400. The pattern on the surface of the mask layer 400 is transferred to the chromium film layer 300, forming the chromium film nanostructure 301 on the chromium film layer 300. After removing the mask layer 400, the gap between two adjacent chromium film nanostructures 301 is used as the etching area 500. Etching gas enters the chromium film layer 300 from the etching area 500 and etches the portion of the titanium dioxide layer 200 corresponding to the etching area 500 along the thickness direction of the chromium film layer 300. The pattern on the surface of the chromium film layer 300 is transferred to the titanium dioxide layer 200, forming titanium dioxide nanostructures 201 on the titanium dioxide layer 200. Then, the chromium film layer 300 is removed. The etching gas in this embodiment contains Cl2 and C. x H y F zThe etching gas contains chromium (Cr) elements, where 0 < x ≤ 4, y ≥ 0, z ≥ 0, and y and z are not both 0. Since the chromium film layer 300 contains Cr, chlorine or oxygen in the etching gas easily reacts with Cr to form CrCl2, CrCl3, or Cr2O3, etc., which are Cr-containing metal residues. The titanium dioxide layer 200 contains titanium, and C in the etching gas... x H y F z The gas reacts with titanium dioxide to produce TiF4 and other metallic residues containing Ti. x H y F z Gases can easily form fluorocarbon and hydrocarbon residues within the reaction chamber. Cleaning the reaction chamber using the method provided in this invention can efficiently remove these residues.

[0072] The present invention also provides a plasma etching apparatus, comprising: a reaction chamber; a Cl2 gas source and an O2 gas source, both connected to the reaction chamber via gas pipelines; a radio frequency source for exciting the gas in the reaction chamber into plasma; and a controller configured to perform the following steps:

[0073] A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is greater than 1.

[0074] A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is less than 1.

[0075] Example

[0076] The TiO2 blanket is highly sensitive to the environment within the reaction chamber. In this embodiment, the substrate to be processed is a TiO2 blanket. After each TiO2 blanket is etched, it is removed from the reaction chamber. Figure 1 As shown, the reaction chamber is cleaned using the following methods, specifically including:

[0077] S1: A first mixed gas is introduced into the reaction chamber, and the first mixed gas is dissociated into plasma. The first mixed gas contains Cl2, O2, and Ar, wherein Cl2 is dominant, the flow rate of Cl2 is 500 sccm, the flow rate of O2 is 100 sccm, and the flow rate of Ar is 400 sccm. When the first mixed gas is introduced, the pressure in the reaction chamber is 10 mT, the radio frequency power is 2000 W, and the cleaning time for the first mixed gas to dissociate into plasma is 30 s.

[0078] S2: A second mixed gas is introduced into the reaction chamber, dissociating the second mixed gas into plasma. The second mixed gas contains Cl2, O2, and Ar, with O2 being the dominant component. The flow rate of Cl2 is 100 sccm, the flow rate of O2 is 500 sccm, and the flow rate of Ar is 400 sccm. When the second mixed gas is introduced, the pressure inside the reaction chamber is 10 mT, the radio frequency power is 2000 W, and the cleaning time for the second mixed gas to dissociate into plasma is 10 s.

[0079] Excessive residue can lead to an unstable environment within the reaction chamber, resulting in inconsistent etching rates between etching operations. After etching 25 TiO2 wafers, the substrate number was plotted on the x-axis, and the etching rate of that substrate was plotted on the y-axis, yielding... Figure 3 .Depend on Figure 3 As can be seen, the substrate etching rate changes very little. This indicates that cleaning the reaction chamber using the method provided in this embodiment between etching of adjacent substrates can completely remove residues from the reaction chamber, stabilizing the environment within the reaction chamber and ensuring that the substrate etching rate remains stable after multiple etching processes.

[0080] Comparative Example

[0081] Using TiO2 wafers as the substrate, after each TiO2 wafer is etched, it is removed from the reaction chamber. The reaction chamber is then cleaned using the following method: a mixed gas is introduced into the reaction chamber, and the mixed gas is dissociated into plasma. The mixed gas contains Cl2 and Ar, with a Cl2 flow rate of 500 sccm and an Ar flow rate of 400 sccm. The pressure inside the reaction chamber is 10 mT during the introduction of the mixed gas, and the cleaning time for the first dissociation of the mixed gas into plasma is 90 s.

[0082] After etching 25 TiO2 wafers, the substrate number was plotted on the x-axis and the etching rate of that substrate on the y-axis, yielding... Figure 4 .Depend on Figure 4 It can be seen that as the number of substrates etched increases, the substrate etching rate gradually decreases, and the decrease is significant. This indicates that even with Cl2 as the cleaning gas, and each cleaning session lasting up to 90 seconds, sufficient cleaning effect cannot be achieved: the residue in the reaction chamber increases, and the environment in the reaction chamber becomes increasingly unstable.

[0083] The cleaning method provided by this invention has minimal corrosive effect on the reaction chamber. Even if the first mixed gas or the second mixed gas is continuously introduced into the reaction chamber for a prolonged period, it will not cause corrosion. After the introduction of the first mixed gas or the second mixed gas is stopped, the reaction chamber can still continue etching the substrate. The following verifies the corrosive effect of the cleaning method provided by this invention on the reaction chamber.

[0084] Verification Example 1: A SiO2 optical sheet was placed on a base, and a first mixed gas was introduced into the reaction chamber to dissociate the first mixed gas into plasma. The first mixed gas contained Cl2, O2, and Ar, with a Cl2 flow rate of 500 sccm, an O2 flow rate of 100 sccm, and an Ar flow rate of 400 sccm. When the first mixed gas was introduced, the pressure inside the reaction chamber was 10 mT, the RF power was 2000 W, and the cleaning time for the first mixed gas to dissociate into plasma was 600 s. Except for the cleaning time, the method of Verification Example 1 was the same as step S1 of Example 1. After completion, the etching rate on the surface of the SiO2 optical sheet was measured.

[0085] Verification Example 2: A SiO2 optical sheet was placed on a base, and a second mixed gas was introduced into the reaction chamber to dissociate the second mixed gas into plasma. The second mixed gas contained Cl2, O2, and Ar, with a Cl2 flow rate of 100 sccm, an O2 flow rate of 500 sccm, and an Ar flow rate of 400 sccm. When the second mixed gas was introduced, the pressure inside the reaction chamber was 10 mT, the RF power was 2000 W, and the cleaning time for the second mixed gas to dissociate into plasma was 600 s. Except for the cleaning time, the method in Verification Example 1 was the same as step S2 of Example 1. After completion, the etching rate on the surface of the SiO2 optical sheet was measured.

[0086] Verification Example 3: A SiO2 optical sheet was placed on a substrate. A mixed gas containing Cl2, BCl3, and Ar was introduced into the reaction chamber. The flow rate of Cl2 was 500 sccm, the flow rate of BCl3 was 100 sccm, and the flow rate of Ar was 400 sccm. During the introduction of this mixed gas, the pressure inside the reaction chamber was 10 mT, the RF power was 2000 W, and the cleaning time for the mixed gas to dissociate into plasma was 600 s. After completion, the etching rate on the surface of the SiO2 optical sheet was measured.

[0087] A schematic diagram of the bombardment intensity under the process conditions in Examples 1-3 is shown below. Figure 5 As shown. When considering whether the process conditions of the cleaning method are suitable, in addition to verifying whether the reaction by-products can be effectively removed, it is also necessary to minimize the bombardment damage to the sidewalls of the reaction chamber. In order to compare the bombardment intensity of different process conditions, a silicon dioxide substrate was selected as the bombardment target and placed in the reaction chamber for different process conditions. If the etching rate of the silicon dioxide substrate is high, it can be inferred that the degree of corrosion of the reaction chamber will also increase. From the etching rate values, the etching rate of verification examples 1-2 is basically 0, indicating that the surface of the SiO2 wafer in verification examples 1-2 is almost not etched, so the inner wall of the reaction chamber will not be corroded by the introduction of the first mixed gas or the second mixed gas; the mixed gas in verification example 3 contains BCl3, and its etching rate is greater than This indicates that the SiO2 wafer surface in Verification Example 3 was severely etched, meaning the inner wall of the reaction chamber would also corrode to the same extent due to the introduction of the mixed gas. Looking at the convergence of etching rates across the surface, the etching rates in Verification Examples 1-2 converge, indicating that the TiO2 wafer surfaces in Verification Examples 1-2 are flat and uniform, thus the inner wall of the reaction chamber also has stronger uniformity. In Verification Example 3, the etching rates diverge across the surface, with the etching rates at various locations roughly varying from... to The inconsistency indicates that the SiO2 wafer surface in Verification Example 3 was not only severely etched, but the degree of etching varied across different areas, resulting in poor uniformity. Consequently, the corrosion degree on the inner wall of the reaction chamber was also inconsistent. Therefore, the reaction chamber cleaning method provided by this invention features weak ion bombardment, resulting in low corrosion of the reaction chamber. After cleaning, the inner wall of the reaction chamber still exhibits better uniformity, without affecting the continued use of the reaction chamber.

[0088] In summary, this invention discloses a method for cleaning a reaction chamber. After processing a substrate in the reaction chamber, the method cleans the residues within the chamber. The method includes: introducing a first mixed gas into the reaction chamber and dissociating the first mixed gas into plasma, wherein the first mixed gas comprises Cl2 and O2, with a volume ratio of Cl2 to O2 greater than 1; and introducing a second mixed gas into the reaction chamber and dissociating the second mixed gas into plasma, wherein the second mixed gas comprises Cl2 and O2, with a volume ratio of Cl2 to O2 less than 1. Compared to introducing only a single gas, the mixed gas method provided by this invention has high residue removal efficiency and can ensure the stability of the reaction chamber environment. The first mixed gas is predominantly Cl2, used to clean metal residues in the reaction chamber, while the second mixed gas is predominantly O2, used to clean fluorocarbon or hydrocarbon residues in the reaction chamber. Therefore, the method provided by this invention can utilize the same type of gas and adjust the gas flow rate to clean different types of residues in the reaction chamber.

[0089] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for cleaning a reaction chamber, characterized in that, After processing the substrate in the reaction chamber, cleaning the residue in the reaction chamber includes: A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is greater than 1. The first mixed gas, after being dissociated into plasma, is used at least to clean up metal residues in the reaction chamber. A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is less than 1.

2. The reaction chamber cleaning method as described in claim 1, characterized in that, In the first mixed gas, the volume ratio of Cl2 to O2 ranges from 2:1 to 10:

1.

3. The reaction chamber cleaning method as described in claim 1, characterized in that, In the second mixed gas, the volume ratio of Cl2 to O2 ranges from 1:10 to 1:

2.

4. The reaction chamber cleaning method as described in claim 1, characterized in that, The first mixed gas also includes Ar, and the volume ratio of Cl2 to Ar is in the range of 1:4 to 4:

1.

5. The reaction chamber cleaning method as described in claim 1, characterized in that, The second mixed gas also includes Ar, and the volume ratio of Ar to O2 is less than 1.

6. The reaction chamber cleaning method as described in claim 1, characterized in that, The metal residue contains at least one of Cr and Ti elements.

7. The reaction chamber cleaning method as described in claim 6, characterized in that, The metal residue includes any one or more of CrCl2, CrCl3, Cr2O3, Cr, or TiF4.

8. The reaction chamber cleaning method as described in claim 1, characterized in that, The second mixed gas, after dissociating into plasma, is used to clean at least one of the fluorocarbon residues and hydrocarbon residues in the reaction chamber.

9. The reaction chamber cleaning method as described in claim 1, characterized in that, The cleaning time for the first mixed gas to dissociate into plasma is 10-60 s.

10. The reaction chamber cleaning method as described in claim 1, characterized in that, The cleaning time for the second mixed gas to dissociate into plasma is 10-60 s.

11. The reaction chamber cleaning method as described in claim 1, characterized in that, The cleaning time for the first mixed gas to dissociate into plasma is greater than the cleaning time for the second mixed gas to dissociate into plasma.

12. The reaction chamber cleaning method as described in claim 1, characterized in that, The pressure inside the reaction chamber where the first mixed gas dissociates into plasma is 5mT-50mT.

13. The reaction chamber cleaning method as described in claim 1, characterized in that, The pressure inside the reaction chamber where the second mixed gas dissociates into plasma is 10mT-100mT.

14. The reaction chamber cleaning method as described in claim 1, characterized in that, The first mixed gas also includes BCl3, and the volume ratio of BCl3 to Cl2 is less than 0.1:

1.

15. The reaction chamber cleaning method as described in claim 1, characterized in that, The second mixed gas also includes BCl3, and the volume ratio of BCl3 to Cl2 is less than 0.1:

1.

16. The reaction chamber cleaning method as described in claim 1, characterized in that, The substrate comprises, from bottom to top, a substrate layer, a titanium dioxide layer, a chromium film layer, and a mask layer; the substrate is processed in the reaction chamber, including the following steps: An etching gas containing Cl2 and C is introduced. x H y F z Gas, wherein 0 < x ≤ 4, y ≥ 0, z ≥ 0, and y and z do not both take the value of 0; Using the mask layer as a mask, the chromium film layer is etched, and then using the chromium film layer as a mask, the titanium dioxide layer is etched to form a titanium dioxide nanostructure on the substrate.

17. A plasma etching apparatus, characterized in that, include: reaction chamber; The Cl2 gas source and the O2 gas source are connected to the reaction chamber through gas pipelines; A radio frequency source is used to excite the gas in the reaction chamber into plasma; and, The controller is configured to perform the following steps: A first mixed gas is introduced into the reaction chamber and dissociated into plasma. The first mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is greater than 1. A second mixed gas is introduced into the reaction chamber and dissociated into plasma. The second mixed gas includes Cl2 and O2, and the volume ratio of Cl2 to O2 is less than 1.

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