Method of removing etch residue from a plasma reaction chamber

Abstract

The application provides a method for removing etching residues in a plasma reaction cavity, wherein the plasma reaction cavity is provided with an electrostatic chuck, and the method comprises: applying voltage to the electrostatic chuck for multiple times, performing a vacuum cycle strategy after each time of voltage application, and the voltage applied in adjacent two times is different; wherein the vacuum cycle strategy comprises: introducing a protective gas into the plasma reaction cavity until the pressure in the plasma reaction cavity reaches a first set pressure value, and maintaining the first set pressure value for a first preset time; performing vacuum on the plasma reaction cavity until the pressure in the plasma reaction cavity decreases to a second set pressure value, and maintaining the second set pressure value for a second preset time. The application can remove etching by-products in the gap between the focus ring and the electrostatic chuck, ensure that the wafer surface will not form an etching barrier layer due to the etching by-products, greatly improve the problem of wafer etching residue defects, and improve the stability of the etching process.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a method for removing etching residues in a plasma reaction chamber. Background Art

[0002] In the back-end metal wire interconnect etching process, a plasma reaction chamber is often used as a reaction vessel. Compared with traditional reactor types, a plasma reaction chamber has advantages such as high efficiency, speed, and pollution-free, and can provide different reaction gas atmospheres for various experiments. A focus ring (FocusRing) and an electrostatic chuck (ESC) are usually provided in the plasma reaction chamber. The electrostatic chuck uses the principle of electrostatic adsorption to adsorb the wafer, and the focus ring can improve the uniformity of processing. You can refer to Figure 1 , the focusing ring 2 is arranged around the electrostatic chuck 1, and there is a gap between the focusing ring 2 and the electrostatic chuck 1. The etching by-products 3 (such as polymers) generated during the plasma etching process will continue to accumulate in the gap, so that in the subsequent plasma etching process, these accumulated etching by-products 3 will be sputtered onto the surface of the wafer 4 to form an etching barrier layer, such as Figure 1 , Figure 1 The arrows in the figure indicate the sputtering direction of etching byproducts 3, which cause etching residues in the patterned area of ​​wafer 4, affecting the subsequent copper filling process, causing copper wire breakage and device failure. Furthermore, as the operation time increases, focus ring 2 is continuously consumed. Not only does it become thinner, but its inner diameter also increases. This increase in the inner diameter of focus ring 2 increases the gap between focus ring 2 and electrostatic chuck 1, causing more etching byproducts 3 to accumulate in the gap between focus ring 2 and electrostatic chuck 1, forming more etch barriers on wafers undergoing subsequent plasma etching, resulting in even more serious impacts. Summary of the Invention

[0003] The object of the present invention is to provide a method for removing etching residues in a plasma reaction chamber, which can remove etching by-products in the gap between a focusing ring and an electrostatic chuck. Multiple vacuum cycle strategies can completely remove the etching by-products to avoid sputtering of etching by-products onto the wafer surface during the next etching process, thereby ensuring that no etching barrier layer is formed on the wafer surface due to the etching by-products, greatly improving the problem of residual defects in wafer etching, and improving the stability of the etching process, thereby improving the electrical performance of the wafer and the yield of the product, reducing the scrap rate, and saving production costs.

[0004] In order to achieve the above object, the present invention provides a method for removing etching residues in a plasma reaction chamber, wherein an electrostatic chuck is provided in the plasma reaction chamber, and the method comprises:

[0005] applying a voltage to the electrostatic chuck multiple times, executing a vacuum cycle strategy after each application of the voltage, and wherein the voltages applied two adjacent times are different;

[0006] Wherein, the vacuum cycle strategy includes:

[0007] introducing a protective gas into the plasma reaction chamber until the pressure in the plasma reaction chamber reaches a first set pressure value, and maintaining the first set pressure value for a first preset time;

[0008] The plasma reaction chamber is evacuated until the pressure in the plasma reaction chamber drops to a second set pressure value, and the second set pressure value is maintained for a second preset time.

[0009] Optionally, the pressure in the plasma reaction chamber is measured by a pressure gauge connected to the plasma reaction chamber.

[0010] Optionally, the protective gas is an inert gas.

[0011] Optionally, the first set pressure value is 190mT to 210mT, and the second set pressure value is 40mT to 60mT.

[0012] Optionally, the first preset time is the same as the second preset time, and the first preset time is 1.5s to 2.5s.

[0013] Optionally, the step of applying voltage to the electrostatic chuck multiple times includes:

[0014] Step 1: increasing the voltage from the initial voltage in sequence until the voltage reaches a preset positive voltage;

[0015] Step 2: decreasing the voltage from a preset positive voltage in sequence until the voltage drops to a preset negative voltage;

[0016] Step 3: increasing the voltage from a preset negative voltage in sequence until the voltage reaches the initial voltage.

[0017] Optionally, repeat steps 1 to 3 multiple times.

[0018] Optionally, the absolute value of the preset positive voltage is the same as the absolute value of the preset negative voltage.

[0019] Optionally, the increasing value and decreasing value of the voltage each time are equal.

[0020] Optionally, the absolute values ​​of the voltages applied twice adjacently are different, and / or the polarities of the voltages applied twice adjacently are different.

[0021] In summary, the method for removing etching residues in a plasma reaction chamber includes: applying a voltage to the electrostatic chuck multiple times, executing a vacuum cycle strategy after each application of the voltage, and the voltages applied twice adjacently are different; wherein the vacuum cycle strategy includes: introducing a protective gas into the plasma reaction chamber until the pressure in the plasma reaction chamber reaches a first set pressure value, and maintaining the first set pressure value for a first preset time; vacuuming the plasma reaction chamber until the pressure in the plasma reaction chamber drops to a second set pressure value, and maintaining the second set pressure value for a second preset time.

[0022] As configured above, the voltage is applied to the electrostatic chuck multiple times, and the voltages applied twice adjacently are different. After each application of the voltage, a vacuum cycle strategy is executed. The vacuum cycle strategy mainly involves first introducing a protective gas into the plasma reaction chamber and then vacuuming the plasma reaction chamber. In this way, the etching byproducts accumulated in the gap between the focusing ring and the electrostatic chuck can be removed by the circulating airflow in the plasma reaction chamber. At the same time, an electrostatic repulsion is generated between the electrostatic chuck and the etching byproducts. The electrostatic repulsion and the circulating airflow work together to help the etching byproducts discharge from the plasma reaction chamber. The present invention can remove the etching byproducts in the gap between the focusing ring and the electrostatic chuck. Repeated vacuum cycle strategies can completely remove the etching byproducts to avoid sputtering of etching byproducts onto the wafer surface during the next etching process, ensuring that no etching barrier layer is formed on the wafer surface, greatly improving the problem of residual defects in wafer etching, improving the stability of the etching process, thereby improving the electrical performance of the wafer and the yield of the product, reducing the scrap rate, and saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0024] Figure 1 A schematic diagram of the locations of etching byproducts in a plasma reaction chamber in the prior art;

[0025] Figure 2 A schematic diagram of a vacuum cycle strategy for a method of removing etching residues in a plasma reaction chamber according to an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of pressure changes in a vacuum pumping cycle strategy of a method for removing etching residues in a plasma reaction chamber according to an embodiment of the present invention;

[0027] Figure 4A schematic diagram of the gas flow direction of a method for removing etching residues in a plasma reaction chamber according to an embodiment of the present invention;

[0028] Figure 5 A schematic diagram of voltage adjustment in a method for removing etching residues in a plasma reaction chamber according to an embodiment of the present invention;

[0029] Figure 6 A schematic diagram of defects in a wafer in the prior art;

[0030] Figure 7 A schematic diagram of wafer defects in a method for removing etching residues in a plasma reaction chamber according to an embodiment of the present invention.

[0031] The accompanying drawings are numerals as follows:

[0032] 1-Electrostatic chuck; 2-Focus ring; 3-Etching byproducts; 4-Wafer; 5-Defect. DETAILED DESCRIPTION

[0033] In this document, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", "front", "back", "top", "bottom", etc. are used to indicate directions or positional relationships based on the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction and operation. Therefore, they cannot be understood as limiting the present invention.

[0034] The following is a more detailed description of the specific embodiments of the present invention with reference to schematic diagrams. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are greatly simplified and not to exact scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0035] The embodiment of the present invention provides a method for removing etching residues in a plasma reaction chamber. It is understood that an electrostatic chuck 1 is provided in the plasma reaction chamber. When the method of this embodiment is used, no wafer is placed in the plasma reaction chamber. After the etching residues are removed by the method of this embodiment, a wafer is placed in the plasma reaction chamber for processing. The method for removing etching residues in a plasma reaction chamber includes:

[0036] The electrostatic chuck 1 is repeatedly applied with voltage, and a vacuum pumping cycle strategy is executed after each voltage application. It is understood that the vacuum pumping cycle strategy should be executed while maintaining the voltage after each voltage application. Moreover, the voltages applied twice adjacently are different, and changing the voltage is more conducive to removing the etching byproducts 3 in the gap between the focusing ring 2 and the electrostatic chuck 1 and evacuating them from the plasma reaction chamber. The two adjacent voltages applied are different in the following ways: (1) the absolute values ​​of the two adjacent voltages are different, and the polarities can be the same or different; (2) the polarities of the two adjacent voltages are different, and the absolute values ​​can be the same or different.

[0037] The vacuum cycle strategy includes steps F1 and F2. Figure 2 This is a schematic diagram of a vacuum cycle strategy for a method of removing etching residues in a plasma reaction chamber according to an embodiment of the present invention. Figure 1 , step F1 and step F2 are described in detail below.

[0038] Step F1: A shielding gas is introduced into the plasma reaction chamber until the pressure within the plasma reaction chamber reaches a first set pressure value and is maintained at the first set pressure value for a first predetermined time period. It will be appreciated that a pressure gauge is connected to the plasma reaction chamber to measure the pressure within the plasma reaction chamber. Generally, the shielding gas is an inert gas. In this embodiment, for example, an inert gas such as argon, nitrogen, or helium can be used as the shielding gas.

[0039] Specifically, the first set pressure value is 190 mT to 210 mT, and the second set pressure value is 40 mT to 60 mT. In this embodiment, the first set pressure value is set to 200 mT, and the second set pressure value is set to 50 mT.

[0040] Step F2: Evacuate the plasma reaction chamber until the pressure in the plasma reaction chamber drops to a second set pressure value, and maintain the second set pressure value for a second preset time. Furthermore, the first preset time and the second preset time are the same, and the first preset time is 1.5 seconds to 2.5 seconds. In this embodiment, the first preset time and the second preset time can both be 2 seconds.

[0041] For example, you can refer to Figure 3 , Figure 3The figure is a schematic diagram of the pressure change of a vacuum cycle strategy. The method for executing a vacuum cycle strategy includes: introducing a protective gas into the plasma reaction chamber until the pressure in the plasma reaction chamber reaches 200mT, and stably maintaining the pressure in the plasma reaction chamber at 200mT within 2s; then, evacuating the plasma reaction chamber until the pressure in the plasma reaction chamber drops to 50mT, and stably maintaining the pressure in the plasma reaction chamber at 50mT within 2s. It can be understood that the vacuum cycle strategy can be simply summarized as first introducing a protective gas into the plasma reaction chamber, and then evacuating the plasma reaction chamber. While evacuating, the circulating airflow in the plasma reaction chamber can carry away the etching by-products 3 accumulated in the gap between the focusing ring 2 and the electrostatic chuck 1, so as to achieve the purpose of discharging the etching by-products 3 from the plasma reaction chamber. Please refer to Figure 4 , Figure 4 The middle arrow indicates the direction of the airflow. At the same time, an electrostatic repulsive force is generated between the electrostatic chuck 1 and the etching byproducts 3. The electrostatic repulsive force and the circulating airflow work together to help the etching byproducts 3 be discharged from the plasma reaction chamber.

[0042] Furthermore, the step of applying voltage to the electrostatic chuck 1 multiple times includes:

[0043] Step 1: Increase the voltage from the initial voltage until the voltage reaches a preset positive voltage. The initial voltage is not limited, and in this embodiment, the initial voltage can be 0V, for example.

[0044] Step 2: Decrease the voltage from the preset positive voltage in sequence until the voltage drops to the preset negative voltage.

[0045] Step 3: Increase the voltage from the preset negative voltage in sequence until the voltage reaches the initial voltage.

[0046] You can refer to Figure 5 , Figure 5 Schematic diagram of voltage changes from step 1 to step 3 in this embodiment, Figure 5 The abscissas S1, S2 to S21 in FIG represent the order of voltage adjustment.

[0047] It is understandable that by repeating steps 1 to 3 multiple times, the etching byproducts 3 in the gap between the focusing ring 2 and the electrostatic chuck 1 can be completely removed.

[0048] In this embodiment, the absolute values ​​of the preset positive voltage and the preset negative voltage are the same, and the increment and decrement values ​​of the voltage are equal. For example, the preset positive voltage can be in the range of 900V to 2600V, and correspondingly, the preset negative voltage can be in the range of -900V to -2600V. For example, the preset positive voltage can be 2500V, and the preset negative voltage is -2500V.

[0049] In this embodiment, an initial voltage of 0V and a preset positive voltage of 1000V are used as an example, and the voltage increment and decrement values ​​are both 200V each time. In this embodiment, an initial voltage is first applied to the electrostatic chuck 1, for example, the initial voltage is set to 0V. At this voltage, a vacuum pumping cycle strategy is executed. Then, the voltage applied to the electrostatic chuck 1 is increased by 200V. At the increased voltage, a vacuum pumping cycle strategy is executed again. The voltage is gradually increased until it reaches 1000V. The voltage is then decreased by 200V each time until it reaches -1000V. The voltage is then increased by 200V each time until it reaches 0V. The vacuum pumping cycle strategy is executed each time the voltage is adjusted.

[0050] As configured above, voltage is applied to the electrostatic chuck 1 multiple times, and the voltages applied twice adjacently are different. A vacuum cycle strategy is executed after each voltage application. The vacuum cycle strategy mainly involves first introducing a protective gas into the plasma reaction chamber, and then vacuuming the plasma reaction chamber. By doing so, the etching byproducts 3 accumulated in the gap between the focusing ring 2 and the electrostatic chuck 1 can be taken away by the circulating airflow in the plasma reaction chamber. At the same time, an electrostatic repulsion force is also generated between the electrostatic chuck 1 and the etching byproducts 3. The electrostatic repulsion force works together with the circulating airflow to help the etching byproducts 3 be discharged from the plasma reaction chamber. The present invention can remove the etching byproducts in the gap between the focusing ring and the electrostatic chuck. Performing the vacuum cycle strategy multiple times can completely remove the etching byproducts to avoid sputtering of etching byproducts onto the wafer surface during the next etching process, thereby ensuring that no etching barrier layer is formed on the wafer surface. This greatly improves the problem of residual defects in wafer etching, improves the stability of the etching process, thereby improving the electrical performance of the wafer and the yield of the product, reducing the scrap rate, and saving production costs. You can refer to Figure 6 and Figure 7 , Figure 6 A schematic diagram showing defects of a wafer in the prior art is shown. Figure 7 The defect diagram of the wafer of this embodiment shows that Figure 7 5% of defects on the wafer Figure 6 There are a lot fewer defects on the wafer.

[0051] It should be noted that references in the specification to "one embodiment," "an embodiment," "a specific embodiment," "some embodiments," etc., merely indicate that the described embodiment may include a particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the knowledge of persons skilled in the relevant art to implement such feature, structure, or characteristic in conjunction with other embodiments, regardless of whether such feature, structure, or characteristic is explicitly described.

[0052] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. The systems disclosed in the embodiments are described briefly because they correspond to the methods disclosed in the embodiments. For relevant details, refer to the method description.

[0053] It should also be noted that although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or to modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

[0054] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are only used to distinguish the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0055] It should also be understood that the terms described herein are intended to describe particular embodiments only and are not intended to limit the scope of the invention. It should be noted that the singular forms "a" and "an" as used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps as well as secondary devices. All conjunctions used should be understood in their broadest sense. Also, the word "or" should be understood to have the definition of a logical "or" rather than a logical "exclusive or" unless the context clearly indicates otherwise. Furthermore, implementation of the methods and / or apparatus in embodiments of the present invention may include performing selected tasks manually, automatically, or in combination.

Claims

1. A method for removing etching residues in a plasma reaction chamber, wherein an electrostatic chuck is provided in the plasma reaction chamber, characterized in that the method include: applying a voltage to the electrostatic chuck multiple times, executing a vacuum cycle strategy after each application of the voltage, and wherein the voltages applied two adjacent times are different; Wherein, the vacuum cycle strategy includes: introducing a protective gas into the plasma reaction chamber until the pressure in the plasma reaction chamber reaches a first set pressure value, and maintaining the first set pressure value for a first preset time; The plasma reaction chamber is evacuated until the pressure in the plasma reaction chamber drops to a second set pressure value, and the second set pressure value is maintained for a second preset time.

2. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The pressure in the plasma reaction chamber is measured by a pressure gauge connected to the plasma reaction chamber.

3. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The protective gas is an inert gas.

4. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The first set pressure value is 190mT to 210mT, and the second set pressure value is 40mT to 60mT.

5. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The first preset time is the same as the second preset time, and the first preset time is 1.5s to 2.5s.

6. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The step of applying voltage to the electrostatic chuck multiple times includes: Step 1: increasing the voltage from the initial voltage in sequence until the voltage reaches a preset positive voltage; Step 2: decreasing the voltage from a preset positive voltage in sequence until the voltage drops to a preset negative voltage; Step 3: increasing the voltage from a preset negative voltage in sequence until the voltage reaches the initial voltage.

7. The method for removing etching residues in a plasma reaction chamber according to claim 6, wherein: Repeat steps 1 to 3 several times.

8. The method for removing etching residues in a plasma reaction chamber according to claim 6, wherein: The absolute value of the preset positive voltage is the same as the absolute value of the preset negative voltage.

9. The method for removing etching residues in a plasma reaction chamber according to claim 6, wherein: The voltage increment value and the voltage decrement value are equal.

10. The method for removing etching residues in a plasma reaction chamber according to claim 1, wherein: The absolute values ​​of the voltages applied twice adjacently are different, and / or the polarities of the voltages applied twice adjacently are different.

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