A plasma processing device and a plasma processing method

Abstract

The present invention discloses a plasma processing device and a processing method, including a reaction chamber, wherein the reaction chamber includes: an air intake device for conveying a clean gas to the reaction chamber; a radio frequency power supply for dissociating the clean gas into a clean plasma; a clean wafer having a first diameter; and an electrostatic chuck for carrying the clean wafer, having a second diameter, wherein the difference between the first diameter and the second diameter is less than or equal to ±0.5 mm. In the present invention, a clean wafer having a size close to that of the electrostatic chuck 110 is used to cover the surface of the electrostatic chuck in the cleaning step, which can effectively reduce the degree of damage to the upper surface of the electrostatic chuck by the clean plasma. At the same time, the clean wafer will not block the second upper surface 134 of the focusing ring and the gap between the focusing ring and the electrostatic chuck, so that the clean plasma can effectively remove the deposits on the second upper surface of the focusing ring and in the gap.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor equipment, and in particular to the field of plasma cleaning technology. Background Art

[0002] In the manufacturing process of semiconductor devices, plasma etching is a key process for processing wafers into designed patterns.

[0003] In a typical plasma etching process, process gases (such as CF4, O2, etc.) form plasma under the action of radio frequency (RF) in the reaction chamber. These plasmas physically bombard and chemically react with the wafer surface, thereby etching a wafer with a specific structure.

[0004] After the wafer etching is completed, the wafer is taken out by a mobile robot. In order to ensure the uniformity of wafer processing in different batches, the reaction chamber needs to be plasma cleaned after the wafer is moved out of the reaction chamber. Clean gas is introduced into the reaction chamber, and radio frequency is applied to excite the above-mentioned clean gas into clean plasma. Under the action of the electric field, the clean plasma bombards the surface of the components in the reaction chamber exposed to the plasma, cleans the deposits that may be generated in the previous etching step, and discharges the clean gas and deposit particles out of the reaction chamber through a vacuum device.

[0005] With the development of technology, thicker deposits will be produced on the surface of parts during some etching processes. In the cleaning step, in order to ensure the cleaning effect of the deposits, a relatively high-power radio frequency signal needs to be applied to the electrostatic chuck. Since the electrostatic chuck is exposed to the cleaning plasma, some areas may be bombarded by the cleaning plasma and damaged, which is not conducive to the stable operation of the plasma processing device. Therefore, it is necessary to provide a plasma processing device that can work stably in the cleaning step. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a plasma processing device and a processing method: A plasma processing device includes a reaction chamber, wherein the reaction chamber includes:

[0007] An air inlet device, used for delivering clean gas to the reaction chamber;

[0008] A radio frequency power source for dissociating the cleaning gas into a cleaning plasma;

[0009] a clean wafer having a first diameter;

[0010] The electrostatic chuck is used to carry the clean wafer and has a second diameter, and the difference between the first diameter and the second diameter is less than or equal to ±0.5 mm.

[0011] Optionally, the difference between the first diameter and the second diameter is less than ±0.2 mm.

[0012] Optionally, the first diameter and the second diameter are the same.

[0013] Optionally, a focusing ring is disposed on the periphery of the electrostatic chuck, and a first gap is disposed between the focusing ring and the electrostatic chuck, and a width of the first gap is greater than or equal to 0.2 mm.

[0014] Optionally, the focusing ring includes a first upper surface and a second upper surface, the first upper surface is higher than the upper surface of the cleaning wafer, and the second upper surface is lower than or level with the lower surface of the cleaning wafer.

[0015] Optionally, when the cleaning wafer is located above the electrostatic chuck, the first gap and the second upper surface are exposed.

[0016] Optionally, an insertion ring is provided below the focusing ring, a second gap is provided between the insertion ring and the electrostatic chuck, and a width of the second gap is less than or equal to a width of the first gap.

[0017] Optionally, the lower surface of the focusing ring and the upper surface of the insert ring are provided with steps that match each other.

[0018] Optionally, the material of the cleaning wafer includes at least one of silicon, silicon carbide and dielectric material.

[0019] Optionally, the electrostatic chuck includes an electrostatic adsorption layer, a base, and a bonding layer connecting the electrostatic adsorption layer and the base, and a protective ring is arranged around the bonding layer.

[0020] Furthermore, the present invention also discloses a plasma processing method, which is performed in the plasma processing device described above and comprises the following steps:

[0021] After the etching process is completed, the etched wafer is moved out of the reaction chamber;

[0022] Moving the clean wafer into the reaction chamber and placing it above the electrostatic chuck;

[0023] Supplying a cleaning gas into the reaction chamber, applying radio frequency power to excite the cleaning gas into a cleaning plasma, wherein the cleaning plasma cleans an area in the reaction chamber that is exposed to the plasma;

[0024] The cleaned wafer is removed.

[0025] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0026] In the present invention, a cleaning wafer having a size close to that of the electrostatic chuck is used to cover the surface of the electrostatic chuck in the cleaning step, which can effectively reduce the degree of damage to the upper surface of the electrostatic chuck caused by the cleaning plasma. At the same time, the cleaning wafer will not block the second upper surface of the focusing ring and the gap between the focusing ring and the electrostatic chuck, so that the cleaning plasma can effectively remove the sediments on the second upper surface of the focusing ring and in the gap. The uniformity of wafer processing by the plasma processing device is ensured, while the arc discharge phenomenon that may be caused by the sediments is reduced, and the stability of the equipment is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0028] Figure 1 A schematic diagram of the structure of a plasma processing device is shown;

[0029] Figure 2 The etching step is shown Figure 1 A partial enlarged view of the middle A area;

[0030] Figure 3 Shows the cleaning steps Figure 1 A partial enlarged view of the middle A area;

[0031] Figure 4 A partial enlarged view of area A after the cleaning step is completed is shown. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Figure 1 A plasma processing device is shown, including a reaction chamber, wherein the reaction chamber includes an upper electrode assembly and a lower electrode assembly arranged opposite to each other, wherein the upper electrode assembly includes a gas shower head 120 and an upper grounding ring 122 arranged around the gas shower head, wherein the gas shower head is used to transport process gas or cleaning gas into the reaction chamber and serves as an upper electrode of the vacuum reaction chamber. The reaction chamber also includes a lifting ring 124, which surrounds the area between the upper electrode assembly and the lower electrode assembly to form a uniform and stable plasma processing space. Figure 1 The plasma processing device shown is a capacitively coupled plasma processing device, and the solution described in the present invention is also applicable to an inductively coupled plasma processing device.

[0034] The lower electrode assembly includes an electrostatic chuck 110, which includes an electrostatic adsorption layer 112, a base 116, and a bonding layer 114 connecting the electrostatic adsorption layer and the base, and a protective ring 182 is arranged around the outer periphery of the bonding layer. The protective ring 182 can protect the bonding layer from damage by plasma, and at the same time, the gap between the focusing ring and the insertion ring and the electrostatic chuck can be separated to reduce arc discharge in the gap. The electrostatic chuck is used to carry the wafer 115 and also serves as the lower electrode of the vacuum reaction chamber, and a reaction area is formed between the upper electrode and the lower electrode. At least one radio frequency power supply 190 is applied to one of the upper electrode or the lower electrode through a matching network, and a radio frequency electric field is generated between the upper electrode and the lower electrode to dissociate the reaction gas into plasma, and the plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. The above-mentioned active particles can undergo various physical and chemical reactions with the surface of the substrate to be processed, so that the morphology of the wafer surface changes, that is, the wafer is etched. An exhaust device (not shown in the figure) is also provided below the vacuum reaction chamber to discharge the reaction by-products out of the reaction chamber and maintain the vacuum environment of the reaction chamber.

[0035] An edge ring assembly is disposed around the periphery of the electrostatic chuck 110. The edge ring assembly specifically includes a focus ring 130, a cover ring 140 disposed around the periphery of the focus ring, and an insert ring 150 disposed below the focus ring. The focus ring 130, the cover ring 140, and the insert ring 150 are used to adjust the electric field or temperature distribution around the wafer to improve the uniformity of substrate processing. An isolation ring 170 is disposed below the insert ring 150. The isolation ring 170 is disposed around the base 116 to control the temperature of the insert ring and isolate the base. The edge ring assembly also includes a plasma confinement ring 160 disposed around the insert ring 150 and the isolation ring 170. The plasma confinement ring is used to form an exhaust channel and confine the plasma within the plasma processing space. The base 116 is usually made of metal, and the edge ring assembly is usually made of dielectric material or semiconductor material. In order to prevent the base 116 from expanding due to heat during the process and causing compression of the edge ring assembly, a gap 185 is usually provided between the electrostatic chuck and the edge ring assembly when the electrostatic chuck 110 and the edge ring assembly are installed at room temperature. See Figure 2 The width of the gap is determined according to factors such as the material of the base and edge ring assembly and the possible operating temperature of the lower electrode assembly, and is usually set between 0.1 mm and 0.5 mm.

[0036] When normal plasma treatment is performed on wafer 115, wafer 115 is moved into the reaction chamber and placed above the electrostatic chuck, where it is fixed and temperature-controlled under the adsorption of the electrostatic chuck. In order to achieve accurate positioning of the wafer when it is placed above the electrostatic chuck, a positioning notch is set in the edge area of ​​the conventional wafer. In order to prevent the positioning notch from exposing part of the electrostatic chuck during the etching process, causing the exposed area of ​​the electrostatic chuck to be damaged by plasma, the diameter of wafer 115 is usually larger than the diameter of electrostatic chuck 110.

[0037] Figure 2 The etching step is shown Figure 1 A partial enlarged view of the A area, according to Figure 2 As shown, the focusing ring 130 includes a first upper surface 132 and a second upper surface 134. When the wafer 115 is placed above the electrostatic chuck, the level of the first upper surface 132 is higher than the level of the upper surface of the wafer 115, and the level of the second upper surface 134 is lower than or flush with the level of the lower surface of the wafer 115. Therefore, during the etching process, the edge area of ​​the wafer 115 at least partially covers the second upper surface 134 of the focusing ring and the gap between the focusing ring and the electrostatic chuck.

[0038] Nevertheless, during the etching process, while the plasma etches the topography of the wafer surface, it also forms deposits on the surfaces of components exposed to the plasma, including the back side of the wafer 115, the two upper surfaces of the focus ring 130, and the gap 185 between the focus ring and the electrostatic chuck. Figure 2 The second upper surface 134 of the middle focusing ring and the black lines in the gap 185 are schematic diagrams of being covered and filled with deposits. After the etching process is completed, the wafer 115 is moved out of the reaction chamber by the mobile robot. In order to ensure the etching uniformity of different wafers, a plasma cleaning step is performed in the reaction chamber after each etching process. In the plasma cleaning step, the wafer is usually not placed on the surface of the electrostatic chuck. The electrostatic chuck and other surfaces exposed to the plasma processing space are removed by chemical reaction or physical bombardment under the action of the cleaning plasma.

[0039] As the process develops, the inventors have found that some processes will produce thicker deposits during the etching process. In order to effectively remove these deposits, it is necessary to apply a greater RF power to the lower electrode assembly or the upper electrode assembly. A greater RF power means a stronger plasma bombardment, which will cause more serious damage to the upper surface of the electrostatic chuck exposed to the plasma. In addition, if there are deposits in the gap between the focusing ring and the electrostatic chuck, since the deposits are usually loose, arc discharge is likely to occur during the etching process, causing damage to the side of the electrostatic chuck.

[0040] Figure 3Shown in the cleaning step Figure 1 A partial enlarged view of the A area in the middle shows a plasma processing device, which can be used for both plasma etching and plasma cleaning steps. The reaction chamber of the device includes an air inlet device, namely the gas shower head 120 described above, which is used to deliver clean gas to the reaction chamber; a radio frequency power supply 190, which is used to dissociate the clean gas into clean plasma; a clean wafer 215, which has a first diameter; and an electrostatic chuck 110, which is used to carry the clean wafer 215, and has a second diameter, and the difference between the first diameter and the second diameter is less than or equal to ±0.5mm. In the present invention, a clean wafer with a size close to that of the electrostatic chuck 110 is used to cover the surface of the electrostatic chuck in the cleaning step, which can effectively reduce the degree of damage to the upper surface of the electrostatic chuck by the clean plasma. At the same time, the clean wafer will not block the second upper surface 134 of the focusing ring and the gap between the focusing ring and the electrostatic chuck, so that the clean plasma can effectively remove the deposits on the second upper surface of the focusing ring and in the gap. The uniformity of wafer processing by the plasma processing device is ensured.

[0041] The present invention limits the difference between the first diameter and the second diameter to be less than or equal to ±0.5 mm. When the first diameter of the cleaning wafer 215 is less than or equal to the second diameter of the electrostatic chuck by 0.5 mm, the cleaning wafer 215 covers most of the upper surface of the electrostatic chuck, which can effectively protect the electrostatic chuck from being damaged by the bombardment of the cleaning plasma. When the first diameter of the cleaning wafer 215 is greater than or equal to the second diameter of the electrostatic chuck by 0.5 mm, it can avoid blocking the second upper surface 134 of the focusing ring, so that the second upper surface 134 of the focusing ring can effectively remove deposits.

[0042] Optionally, the difference between the first diameter and the second diameter is less than ±0.2 mm, which can better cover the surface of the electrostatic chuck while reducing the obstruction of the gap between the focusing ring and the electrostatic chuck. As known above, the gap between the focusing ring and the electrostatic chuck is usually set to between 0.1 mm and 0.5 mm. Therefore, in order to ensure that at least part of the gap is exposed to the cleaning plasma, when the first diameter is greater than the second diameter, the difference between the first diameter and the second diameter is limited to be less than or equal to 0.2 mm. Optionally, the diameter size of the cleaning wafer 215 can be set to be equal to the diameter size of the electrostatic chuck.

[0043] Figure 4 A partial enlarged view of area A after the cleaning step is completed is shown. Figure 4It can be seen that after adopting the cleaning wafer 215 of the present invention, even if a large RF power is applied to the reaction chamber for cleaning, the surface of the electrostatic chuck will not be damaged. At the same time, since the diameter of the cleaning wafer is close to the diameter of the electrostatic chuck, the second upper surface 134 of the focusing ring and the gap 185 will not be covered, so that the cleaning plasma can more effectively remove the deposits on the second upper surface 134 of the focusing ring and the gap 185, avoiding the arc discharge that may occur in the deposits and ensuring the consistency of wafer processing in the reaction chamber.

[0044] As mentioned above, an insert ring 150 is provided below the focus ring 130, and a gap is also provided between the insert ring and the electrostatic chuck, and the width of the gap is equal to or less than the width of the gap between the focus ring and the electrostatic chuck. The gap between the edge ring assembly and the electrostatic chuck is a high-incidence area for arc discharge. The larger the gap width, the lower the tolerance to the RF voltage applied to the reaction chamber, and the more likely arc discharge will occur. Therefore, under the premise of meeting the installation requirements and bearing the expansion of the base, the gap 185 is set as small as possible.

[0045] In addition, the lower surface of the focus ring 130 and the upper surface of the insert ring 150 may be provided with mutually matching steps. The provision of the steps can prevent the gap between the focus ring and the insert ring from being connected to the gap 185, and prevent the arc discharge that may occur in the gap 185 from penetrating into the gap between the focus ring and the insert ring, thereby protecting the focus ring and the insert ring.

[0046] The material of the clean wafer 215 used in the present invention can be the same as that of the conventional wafer 115. Optionally, the material of the clean wafer includes at least one of silicon, silicon carbide and dielectric material, with the main consideration being not to introduce contamination during the cleaning step.

[0047] The present invention further discloses a plasma treatment method, which comprises the following steps:

[0048] After the etching process is completed, the etched wafer 115 is moved out of the reaction chamber;

[0049] Moving the clean wafer 215 into the reaction chamber and placing it on the electrostatic chuck;

[0050] Supplying a cleaning gas into the reaction chamber, applying radio frequency power to excite the cleaning gas into a cleaning plasma, wherein the cleaning plasma cleans an area in the reaction chamber that is exposed to the plasma;

[0051] The clean wafer 215 is removed.

[0052] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A plasma processing device, comprising a reaction chamber, characterized in that: The reaction chamber comprises: An air inlet device, used for delivering clean gas to the reaction chamber; A radio frequency power source for dissociating the cleaning gas into a cleaning plasma; A cleaning wafer having a first diameter, wherein a material of the cleaning wafer comprises at least one of silicon, silicon carbide and a dielectric material; An electrostatic chuck, used for carrying the clean wafer, having a second diameter, and a difference between the first diameter and the second diameter is less than or equal to ±0.2 mm; A focusing ring is arranged around the electrostatic chuck, a first gap is arranged between the focusing ring and the electrostatic chuck, the width of the first gap is greater than or equal to 0.2 mm, and the first gap is at least partially exposed when the cleaning wafer is located above the electrostatic chuck.

2. The plasma processing apparatus according to claim 1, wherein: The first diameter and the second diameter are the same.

3. The plasma processing apparatus according to claim 1, wherein: The focus ring includes a first upper surface and a second upper surface, wherein the first upper surface is higher than the upper surface of the cleaning wafer, and the second upper surface is lower than or level with the lower surface of the cleaning wafer.

4. The plasma processing apparatus according to claim 3, wherein: The cleaning wafer exposes the second upper surface when located above the electrostatic chuck.

5. The plasma processing apparatus according to claim 1, wherein: An insert ring is arranged below the focusing ring, a second gap is arranged between the insert ring and the electrostatic chuck, and a width of the second gap is less than or equal to a width of the first gap.

6. The plasma processing apparatus according to claim 5, characterized in that: The lower surface of the focusing ring and the upper surface of the inserting ring are provided with steps which match each other.

7. The plasma processing apparatus according to claim 1, wherein: The electrostatic chuck comprises an electrostatic adsorption layer, a base and a bonding layer connecting the electrostatic adsorption layer and the base, and a protective ring is arranged around the outer periphery of the bonding layer.

8. A plasma treatment method, characterized in that: The method is performed in a plasma processing device according to any one of claims 1 to 7, and comprises the following steps: After the etching process is completed, the etched wafer is moved out of the reaction chamber; Moving the clean wafer into the reaction chamber and placing it above the electrostatic chuck; Supplying a cleaning gas into the reaction chamber, applying radio frequency power to excite the cleaning gas into a cleaning plasma, wherein the cleaning plasma cleans an area in the reaction chamber that is exposed to the plasma; The cleaned wafer is removed.

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