A clean wafer, plasma processing device and processing method

Abstract

The present invention discloses a clean wafer, a plasma processing device and a processing method, comprising a reaction chamber, wherein the reaction chamber comprises: an air intake device for conveying clean gas to the reaction chamber; a radio frequency power supply for dissociating the clean gas into clean plasma; a clean wafer; an electrostatic chuck for carrying the clean wafer, a support device is arranged between the clean wafer and the electrostatic chuck, the support device forms a certain height between the back of the clean wafer and the surface of the electrostatic chuck, and then forms a certain gap between the back of the edge area of ​​the clean wafer and the upper surface of the focus ring, avoiding blocking of the upper surface of the focus ring and the gap between the focus ring and the electrostatic chuck, so that the clean plasma can effectively remove the sediments on the second upper surface of the focus 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 sediment is reduced, and the stability of the equipment is improved.

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, the plasma processing device includes a reaction chamber, 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] Cleaning wafers;

[0010] An electrostatic chuck for carrying the clean wafer;

[0011] A plurality of supporting devices are arranged between the cleaning wafer and the electrostatic chuck, and the supporting devices are fixedly connected to the cleaning wafer.

[0012] Optionally, the supporting device is a plurality of supporting platforms arranged on the back side of the cleaning wafer, and the supporting platforms form a gap with a first height between the cleaning wafer and the electrostatic chuck.

[0013] Optionally, the first height ranges from greater than 0 to less than or equal to 5 mm.

[0014] Optionally, the support platform and the cleaning wafer are made integrally or fixedly connected by bonding.

[0015] Optionally, the distance from the support platform to the center of the cleaning wafer is smaller than the radius of the electrostatic chuck.

[0016] Optionally, the support platform is two or more discontinuous support platforms, and the multiple discontinuous support platforms have the same height.

[0017] Optionally, the support platform is a continuous structure to achieve stable support for the clean wafer.

[0018] Optionally, the cleaning wafer has a first diameter, the electrostatic chuck has a second diameter, and the first diameter is greater than or equal to the second diameter.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] Optionally, the lower surface of the focusing ring and the upper surface of the insert ring are provided with steps that match each other.

[0023] Optionally, the material of the cleaning wafer is the same as or different from the material of the supporting device.

[0024] The present invention also discloses a cleaning wafer, which is used to be moved into a reaction chamber in a plasma cleaning process and cover the upper surface of an electrostatic suction cup in the reaction chamber. At least one supporting platform is arranged on the back of the cleaning wafer, and the supporting platform is integrally manufactured with the cleaning wafer or fixed by bonding.

[0025] The present invention also discloses a plasma processing method, which is performed in the plasma processing device described above and comprises the following steps:

[0026] After the etching process is completed, the etched wafer is moved out of the reaction chamber;

[0027] Moving the clean wafer into the reaction chamber and placing it above the electrostatic chuck;

[0028] 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 the area in the reaction chamber exposed to the plasma, the second upper surface of the focus ring below the edge area of ​​the clean wafer, and the gap between the focus ring and the electrostatic chuck;

[0029] The cleaned wafer is removed.

[0030] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0031] The present invention uses a cleaning wafer to cover the surface of the electrostatic chuck in the cleaning step to reduce the damage of the high-power cleaning plasma to the upper surface of the electrostatic chuck. At the same time, a supporting device is arranged between the cleaning wafer and the electrostatic chuck, and the supporting device forms a certain height between the back of the cleaning wafer and the surface of the electrostatic chuck, so that a certain gap is formed between the back of the edge area of ​​the cleaning wafer and the second upper surface of the focusing ring, avoiding blocking of 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 the wafer processing by the plasma processing device is ensured, while the arc discharge phenomenon that may be caused by the sediment is reduced, and the stability of the equipment is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] Figure 1 A schematic diagram of the structure of a plasma processing device is shown;

[0034] Figure 2 The etching step is shown Figure 1 A partial enlarged view of the middle A area;

[0035] Figure 3 Shows the cleaning steps Figure 1A partial enlarged view of the middle A area;

[0036] Figure 4 A partial enlarged view of area A after the cleaning step is completed is shown;

[0037] Figure 5 A schematic diagram showing the dimensions of a cleaning wafer, an electrostatic chuck, and a supporting device on the cleaning wafer;

[0038] Figure 6 A schematic structural diagram of a support device on a cleaning wafer according to another embodiment is shown. DETAILED DESCRIPTION

[0039] 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.

[0040] 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.

[0041] 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. A protective ring 182 is arranged around the bonding layer (see Figure 2). The protective ring 182 can protect the bonding layer from damage by the plasma, and at the same time can separate the gap between the focusing ring and the insertion ring and the electrostatic chuck 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. 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 a variety of 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.

[0042] 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, such as greater than or equal to 0.2 mm.

[0043] When the wafer 115 is subjected to normal plasma treatment, the 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 the wafer 115 is usually larger than the diameter of the electrostatic adsorption layer 112.

[0044] 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.

[0045] Nevertheless, during the etching process, while the plasma etches the topography of the wafer surface, deposits are also formed on the surfaces of the components exposed to the plasma, including the back side of the edge region 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 black lines in the second upper surface 134 and the gap 185 of the middle focusing ring are shown as schematic diagrams 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 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. In the plasma cleaning step, the wafer is usually not placed on the surface of the electrostatic chuck so that the cleaning plasma can remove the deposits on the second upper surface 134 and the gap 185 of the focusing ring.

[0046] 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.

[0047] Figure 3 Shown in the cleaning step Figure 1 A partial enlarged view of area A in the middle. Figure 1The plasma processing device shown can be applied to both plasma etching step and plasma cleaning step. The reaction chamber of the device includes an inlet device, namely the gas shower head 120 described above, for delivering cleaning gas to the reaction chamber; a radio frequency power supply 190, for dissociating the cleaning gas into cleaning plasma; a cleaning wafer 215, having a first diameter; an electrostatic chuck 110, for carrying the cleaning wafer 215, and a supporting device 216 is provided between the electrostatic chuck 110 and the cleaning wafer 215. The supporting device 216 allows a first height h to exist between the back of the cleaning wafer and the upper surface of the electrostatic chuck in the cleaning step, and the first height forms a gap between the edge area of ​​the cleaning wafer 215 and the second upper surface 134 of the focus ring, thereby allowing the cleaning plasma to enter the gap to clean the deposits on the second upper surface 134 of the focus ring and the deposits in the gap 185 between the focus ring and the electrostatic chuck. The height range of the supporting device 216 is greater than 0 and less than or equal to 5 mm. Since the distance between the cleaning wafer and the electrostatic chuck needs to be controlled within the thickness range of the plasma sheath, in order to prevent the generation of plasma between the cleaning wafer and the electrostatic chuck during the cleaning step and damage to the surface of the electrostatic chuck, the height of the support device needs to be set to be less than or equal to 5 mm. At the same time, at this height, the upper surface edge area of ​​the electrostatic chuck can be effectively prevented from being damaged by high-energy ions incident at an oblique angle.

[0048] After the cleaning step is completed, the support device 216 needs to be moved out of the reaction chamber together with the clean wafer, so the support device 216 needs to be fixedly connected to the clean wafer. In one embodiment, the support device 216 is made integrally with the clean wafer 215, and the material of the support device is the same as the material of the clean wafer, for example, at least one of silicon, silicon carbide and dielectric material. In another embodiment, the support device 216 can be made separately from the clean wafer and then fixed by bonding or the like. In this embodiment, the material of the support device and the clean wafer can be the same or different. For example, the material of the support device can be ceramic, Teflon, etc., with the main consideration being not to introduce contamination during the cleaning step.

[0049] In order to prevent the existence of areas on the surface of the electrostatic chuck that are not covered by the cleaning wafer, the diameter of the cleaning wafer used in the present invention is greater than or equal to the diameter of the electrostatic chuck. At this time, when a high-power RF power supply is applied to the reaction chamber, the deposits on the second upper surface 134 of the focusing ring and the deposits in the gap 185 between the focusing ring and the electrostatic chuck can be effectively cleaned, thereby ensuring the uniformity of wafer processing by the plasma processing device and reducing the degree of damage to the upper surface of the electrostatic chuck caused by the cleaning plasma.

[0050] 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 supporting device 216 is arranged between the cleaning wafer and the electrostatic chuck, the cleaning wafer will not cover the second upper surface 134 and the gap 185 of the focusing ring, so that the cleaning plasma can more effectively remove the deposits on the second upper surface 134 and the gap 185 of the focusing ring, avoiding the arc discharge that may occur in the deposits, and ensuring the consistency of wafer processing in the reaction chamber.

[0051] Figure 5 A schematic diagram showing the dimensions of a cleaning wafer, an electrostatic chuck, and a supporting device on the cleaning wafer is shown. Figure 5 , the diameter of the cleaning wafer 215 is greater than the diameter of the electrostatic chuck 110. In other embodiments, the diameter of the cleaning wafer 215 may be equal to the diameter of the electrostatic chuck 110 to achieve complete coverage of the upper surface of the electrostatic chuck. Avoid high-power cleaning plasma from damaging the electrostatic chuck. Since the support device 216 is to be placed on the surface of the electrostatic chuck, the distance from the support device to the center of the cleaning wafer is less than the radius of the electrostatic chuck to form a height h between the cleaning wafer and the electrostatic chuck.

[0052] Figure 5 The support device 216 shown is three discontinuous support platforms. In order to ensure the stable fixation of the clean wafer, the multiple discontinuous support platforms have the same height. It can be imagined that in other embodiments, the number of support devices 216 can be more than three. In this case, it is necessary to note that the multiple support platforms cannot hinder the lifting of the clean wafer by the lifting mechanism in the base and the removal of the clean wafer by the robot arm. At the same time, the stable fixation of the clean wafer can achieve the purpose of the present invention.

[0053] In another embodiment, Figure 6 As shown, the supporting device can be two supporting platforms 316. In order to achieve stable fixation of the clean wafer 315, the supporting platform in this embodiment can have a certain length. It can be imagined that in other embodiments, the supporting device can be a continuous supporting platform in an annular, semi-annular or other shapes. At this time, it should be noted that the continuous supporting platform cannot hinder the lifting of the clean wafer by the lifting mechanism in the base and the removal of the clean wafer by the robot arm. At the same time, the stable fixation of the clean wafer can achieve the purpose of the present invention.

[0054] As described above, an insert ring 150 is provided below the focusing ring 130, and a gap is also provided between the insert ring and the electrostatic chuck, the width of which is equal to or smaller than the width of the gap between the focusing 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 between the insert ring and the electrostatic chuck is set as small as possible.

[0055] 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.

[0056] 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.

[0057] The present invention further discloses a cleaning wafer, which is used to be moved into a reaction chamber in a plasma cleaning process and cover the upper surface of an electrostatic chuck in the reaction chamber. At least one supporting device is arranged on the back of the cleaning wafer, and the supporting device is integrally manufactured with the cleaning wafer or fixed by bonding.

[0058] The present invention further discloses a plasma treatment method, which comprises the following steps:

[0059] After the etching process is completed, the etched wafer 115 is moved out of the reaction chamber;

[0060] Moving the clean wafer 215 into the reaction chamber and placing it on the electrostatic chuck;

[0061] 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 the area in the reaction chamber exposed to the plasma, the second upper surface of the focus ring below the edge area of ​​the clean wafer, and the gap between the focus ring and the electrostatic chuck;

[0062] The clean wafer 215 is removed.

[0063] 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; An electrostatic chuck, used to carry a clean wafer, wherein the diameter of the clean wafer is greater than or equal to the diameter of the electrostatic chuck; A plurality of supporting devices are arranged between the cleaning wafer and the electrostatic chuck, and the supporting devices are fixedly connected to the cleaning wafer; A focusing ring is arranged on the periphery of the electrostatic chuck, 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 clean wafer, the second upper surface is lower than or level with the lower surface of the clean wafer, the supporting device forms a gap between the edge area of ​​the clean wafer and the second upper surface, the cleaning plasma can enter the gap, the supporting device is a supporting platform arranged on the back of the clean wafer, the supporting platform forms a gap with a first height between the clean wafer and the electrostatic chuck, and the range of the first height is greater than 0 and less than or equal to 5 mm.

2. The plasma processing apparatus according to claim 1, wherein: The support platform and the cleaning wafer are made in one piece or fixedly connected by bonding.

3. The plasma processing apparatus according to claim 1, wherein: The distance from the support platform to the center of the cleaning wafer is smaller than the radius of the electrostatic chuck.

4. The plasma processing apparatus according to claim 1, wherein: The support platforms are two or more discontinuous support platforms, and the multiple discontinuous support platforms have the same height.

5. The plasma processing apparatus according to claim 1, wherein: The support platform is a continuous structure to achieve stable support for the clean wafer.

6. The plasma processing apparatus according to claim 1, wherein: A first gap is arranged between the focusing ring and the electrostatic chuck, and a width of the first gap is greater than or equal to 0.2 mm.

7. The plasma processing apparatus according to claim 6, 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.

8. The plasma processing apparatus according to claim 7, wherein: The lower surface of the focusing ring and the upper surface of the inserting ring are provided with steps which match each other.

9. The plasma processing apparatus according to claim 1, wherein: The cleaning wafer and the supporting device may be made of the same or different materials.

10. A clean wafer, used in a reaction chamber of a plasma processing device according to any one of claims 1 to 9 and covering the upper surface of an electrostatic chuck in the reaction chamber, characterized in that: At least one supporting platform is arranged on the back of the clean wafer, and the supporting platform is integrally manufactured with the clean wafer or fixed by bonding.

11. A plasma treatment method, characterized in that: The method is performed in a plasma processing device according to any one of claims 1 to 9, 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 and the supporting device into the reaction chamber and placing them 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 the area in the reaction chamber exposed to the plasma, the second upper surface of the focus ring below the edge area of ​​the clean wafer, and the gap between the focus ring and the electrostatic chuck; The clean wafer and the support device are removed.

Images