Cleaning method of electrostatic chuck for wafer

Abstract

The present invention provides a cleaning method for an electrostatic chuck for a wafer, firstly, a control sheet containing an oxide film layer is covered on the electrostatic chuck, then, without supplying a DC voltage and cooling gas to the electrostatic chuck, a cleaning gas injected into a process chamber is excited by radio frequency to generate plasma, and the plasma can convert metal deposits on the electrostatic chuck into a gaseous state, and finally the gaseous metal deposits are discharged from the process chamber. The cleaning method is easy to operate, has high cleaning efficiency and good effect, avoids downtime caused by deposits on the electrostatic chuck, and is conducive to improving the yield of wafer etching.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for cleaning an electrostatic chuck for a wafer. Background Art

[0002] In the semiconductor production process, the electrostatic chuck used to hold the wafer will attach metal deposits during etching. For example, during the tungsten etching process, tungsten disulfide (WS 2 ) Byproducts, since tungsten disulfide is not easy to volatilize, will adhere to the sidewalls and edges of the upper surface of the electrostatic chuck, and will accumulate thicker and thicker with the use time. When the byproducts are deposited to a certain thickness, the electrostatic chuck will find it difficult to hold the wafer, the process back pressure will increase, and the wafer position will easily shift, which will cause the machine to shut down and alarm during the etching process; at the same time, because the wafer is raised by the byproducts, it will affect the etching rate, resulting in low wafer yield. Summary of the invention

[0003] In view of this, an embodiment of the present specification provides a method for cleaning an electrostatic chuck for a wafer, which is used to regularly clean the electrostatic chuck used to adsorb wafers. It is easy to operate, has high cleaning efficiency and good effect, avoids downtime caused by electrostatic chuck cleaning, and is beneficial to improving the yield of wafer etching.

[0004] The embodiments of this specification provide the following technical solutions:

[0005] A method for cleaning an electrostatic chuck for a wafer comprises the following steps:

[0006] Covering the electrostatic chuck with a control sheet containing an oxide film layer;

[0007] Under the condition that a direct current voltage and a cooling gas are not supplied to the electrostatic chuck, a cleaning gas injected into the process chamber is excited by radio frequency to generate plasma, wherein the plasma is used to convert the metal deposit on the electrostatic chuck into a gaseous state;

[0008] The gaseous metal deposits are discharged from the process chamber.

[0009] In the above-mentioned cleaning method of the electrostatic chuck for wafers, a control sheet containing an oxide film layer is placed on the electrostatic chuck, so that the upper surface of the electrostatic chuck can be protected during plasma bombardment to avoid damage to the adsorption surface; at the same time, since no DC voltage and cooling gas are supplied to the electrostatic chuck during the cleaning process, the control sheet will not be adsorbed by the electrostatic chuck, and the plasma can not only convert the metal deposits on the side wall of the electrostatic chuck into a gaseous state, but also the plasma can enter the gap between the control sheet and the electrostatic chuck, convert the metal deposits on the edge of the upper surface of the electrostatic chuck into a gaseous state, and finally be discharged from the process chamber along with the cleaning gas, with high cleaning efficiency, good effect, and easy control and operation.

[0010] The embodiment of the present specification also provides a solution, before the control sheet is covered on the electrostatic chuck, the cleaning method of the electrostatic chuck for the wafer further includes:

[0011] The process chamber is evacuated.

[0012] The embodiment of this specification also provides a solution, the duration of radio frequency excitation of the cleaning gas is 20 to 30 seconds.

[0013] The embodiments of the present specification also provide a solution, wherein the oxide film layer covers the surface of the control sheet facing toward and / or away from the electrostatic chuck.

[0014] The embodiment of this specification also provides a solution, wherein the cleaning gas includes at least one of sulfur hexafluoride and chlorine.

[0015] The embodiment of the present specification also provides a solution, wherein the control piece is circular, and the diameter of the control piece is not less than the diameter of the electrostatic chuck.

[0016] The embodiments of this specification also provide a solution, wherein the frequency of the radio frequency excitation is 13.56 MHz or 27 MHz.

[0017] The embodiments of this specification also provide a solution, wherein the metal deposit includes tungsten disulfide.

[0018] The embodiment of this specification also provides a solution for cleaning the electrostatic chuck after 75 to 125 tungsten etchings.

[0019] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above technical solutions adopted in the embodiments of this specification include at least: the cleaning method of the electrostatic chuck for wafers provided by the present invention, the electrostatic chuck is covered with a control sheet containing an oxide film layer, when plasma bombards, the oxide layer on the control sheet can protect the upper surface of the electrostatic chuck for adsorbing the wafer, and avoid damage to the adsorption surface during the cleaning process, in addition, the control sheet is only placed on the upper surface of the electrostatic chuck, during the cleaning process, the electrostatic chuck does not load a DC voltage, and does not provide cooling gas to the back of the control sheet, the control sheet will not be adsorbed or move freely, and retains contact with the edge of the electrostatic chuck, therefore, the RF-excited plasma can not only vaporize the metal deposits on the side wall of the electrostatic chuck, but also enter between the control sheet and the electrostatic chuck along the gap at the edge of the electrostatic chuck, vaporize the metal deposits at the edge of the electrostatic chuck, thereby comprehensively and effectively removing the metal deposits at various locations of the electrostatic chuck. The above cleaning method has simple operating steps and good cleaning effect, and the cleaned electrostatic chuck can better adsorb the wafer in the etching process, avoid downtime, and improve the yield of wafer etching. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 is a schematic diagram of the formation of metal deposits on the electrostatic chuck during tungsten etching;

[0022] Figure 2 is a schematic diagram of removing metal deposits on an electrostatic chuck in one embodiment of the present invention;

[0023] Among them, 1. process chamber, 2. electrostatic chuck, 21. metal deposit, 3. control sheet, 4. process gas, 5. radio frequency device, 6. control sheet, 7. cleaning gas. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0025] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0026] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspect described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0027] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0028] It should be understood that "the connection between component A and component B" means that component A is directly in contact with component B, or component A is indirectly connected to component B through other components. The directional words such as "upper", "lower", "inner", "outer", and "side" described in the exemplary embodiments of this specification are described from the perspectives shown in the drawings and should not be understood as limiting the exemplary embodiments of this specification.

[0029] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0030] like Figure 1 As shown, referring to the background technology, during the etching process, the process gas 4 enters the process chamber 1 through the through hole on the inner wall of the process chamber 1, and forms a plasma under the excitation of the radio frequency device 5, and the plasma carries high energy for etching the wafer 3. The wafer 3 is adsorbed and fixed on the electrostatic chuck 2. As the etching proceeds, byproducts formed during the etching process will adhere to the side walls and edge positions of the upper surface of the electrostatic chuck 2, such as disulfide generated during tungsten etching. Tungsten disulfide adheres to the electrostatic chuck 2, and the deposition position is shown as the position of the metal deposit 21 on the electrostatic chuck 2. As the etching process time increases, more byproducts will be deposited at the above-mentioned positions, which will have an adverse effect on the etching process, increase the occurrence rate of downtime, and affect the yield of the product.

[0031] In order to solve the above problems, the inventors proposed a cleaning method for an electrostatic chuck for wafers through careful research and repeated exploration. The inventors first used plasma to bombard the metal deposits on the electrostatic chuck, converting them into a gaseous state and discharging them from the process chamber along with the cleaning gas. However, the inventors found that in the process of removing metal deposits, the plasma also bombarded the surface of the electrostatic chuck to which no deposits were attached, causing damage, especially causing unnecessary damage to the upper surface used to carry and fix the wafer. The inventors also proposed using a control sheet to shield the upper surface of the electrostatic chuck, and found that the shielding protection effect of the control sheet with an oxide film layer on the surface is the best. The reason is that the oxide film layer effectively blocks the plasma bombardment, thereby protecting the position on the upper surface of the electrostatic chuck where no deposits are attached, and the oxide film keeps the properties of the control sheet stable, so the control sheet can be reused in the cleaning process. In addition, in order to remove the deposits on the edge of the upper surface of the electrostatic chuck, the inventor also proposed that the control sheet cannot be adsorbed on the electrostatic chuck, so that the plasma can enter the gap between the bottom of the control sheet and the deposits, thereby achieving the purpose of gasification and removal of the deposits; and, cooling gas cannot be provided to the electrostatic chuck to avoid the formation of back pressure under the control sheet and prevent the control sheet from being blown and displaced by the gas. Combining the above operations, the inventor summarizes the cleaning method of the electrostatic chuck as follows: Step 1, convey a control sheet with an oxide film layer into the process chamber; Step 2, control the machine so that no DC voltage and back cooling helium are applied to the electrostatic chuck; Step 3, RF excites the cleaning gas to generate plasma, plasma cleans the electrostatic chuck, and exhausts the gas. Thereby, the vaporized metal deposits are removed from the electrostatic chuck and excluded from the process chamber, thereby achieving the effect of cleaning the electrostatic chuck.

[0032] The technical solutions provided by various embodiments of the present application are described below in conjunction with the accompanying drawings.

[0033] like Figure 2 The cleaning method of the electrostatic chuck for the wafer shown comprises the following steps:

[0034] Step S1, covering the electrostatic chuck 2 with a control sheet 6 containing an oxide film layer;

[0035] It should be noted that the type of the oxide film layer is not limited.

[0036] It should also be noted that the control sheet 6 covers the electrostatic chuck 2, which means that the control sheet 6 is larger than the electrostatic chuck 2 and can shield the electrostatic chuck 2. Usually, the size of the control sheet 6 is slightly larger than the electrostatic chuck 2. In addition, the control sheet 2 can also be a waste wafer containing an oxide film layer.

[0037] Step S2, without supplying a DC voltage and cooling gas to the electrostatic chuck 2, RF excites the clean gas 7 injected into the process chamber 1 to generate plasma, and the plasma is used to convert the metal deposit (not shown in the figure) on the electrostatic chuck 2 into a gaseous state;

[0038] Specifically, the cleaning gas 7 is transported into the process chamber 1 through a pipeline connected to the inner wall of the process chamber 1, and generates plasma under the excitation of the radio frequency device 5. The plasma bombards the metal deposits on the electrostatic chuck 2 and converts the metal deposits into a gaseous state.

[0039] It should be noted that the cooling gas includes various gases represented by helium (He) used to cool the wafer in the etching process. In this step, no cooling gas is provided to the electrostatic chuck 2, that is, no gas is provided on the back of the control plate 6 to prevent the control plate 6 from moving under the action of the air pressure below. In addition, no DC voltage is provided to the electrostatic chuck 2 to prevent the control plate 6 from being adsorbed and to avoid sealing the contact gap between the lower surface of the control plate 6 and the edge of the upper surface of the electrostatic chuck 2, so that the plasma cannot act on the metal deposits inside the gap, affecting the cleaning effect.

[0040] It should also be noted that if a plasma cleaning program is preset in the control program or operation menu of the machine, plasma cleaning can be performed by directly running the program or by setting it in the process menu.

[0041] Step S3, exhausting the gaseous metal deposits from the process chamber.

[0042] It should be noted that an exhaust pipeline (not shown in the figure) is provided in the process chamber 1 , and the exhaust pipeline is connected to an exhaust pump to exhaust the clean gas and gaseous metal deposits after the reaction.

[0043] In the above-mentioned cleaning method of the electrostatic chuck for wafers, when the plasma bombards to remove the metal deposits, the control sheet containing the oxide film layer can protect the upper surface of the electrostatic chuck to avoid damage to the adsorption surface; at the same time, because the control sheet is placed on the electrostatic chuck and does not supply DC voltage and cooling gas to the electrostatic chuck, there is a gap between the control sheet and the oxide film layer, and the plasma can not only contact the metal deposits covered under the control sheet, but also contact the metal deposits on the side of the electrostatic chuck, and convert them into gaseous state, and discharge them from the process chamber with the cleaning gas. With the above-mentioned cleaning method, the normal operation time of the equipment is increased from about 20 hours to 100 hours, the defect rate is reduced by more than 90%, and the cleaning efficiency is high, the effect is good, and it is easy to control and operate.

[0044] In some embodiments, before step S1, the above-mentioned method for cleaning the electrostatic chuck for a wafer further includes:

[0045] Step S0, evacuating the process chamber 1.

[0046] Specifically, Figure 1 and Figure 2 The process chamber 1 shown is also connected to a vacuum pipeline (not shown in the figure), and the vacuum pipeline exhausts the gas in the process chamber 1 through a vacuum device, such as a vacuum pump.

[0047] In some embodiments, a wafer transfer chamber (not shown in the figure) is also provided next to the process chamber 1. When the process chamber 1 is evacuated, the wafer transfer chamber is also evacuated, and then the control chip 6 in the wafer transfer chamber is placed on the electrostatic suction cup 2 by a robotic arm.

[0048] In the above solution, by extracting a vacuum, the air in the process chamber 1 can be discharged more quickly, the intake efficiency of the cleaning gas 7 can be improved, and the duration of the cleaning process can be shortened.

[0049] In some embodiments, after the process chamber 1 is evacuated, during the steps of the aforementioned cleaning method for the electrostatic chuck for the wafer, the working time of the RF device 5 is controlled so that the RF excitation time of the cleaning gas is 20 to 30 seconds.

[0050] In some embodiments, the oxide film layer on the control sheet 6 may only cover the surface of the control sheet 6 facing the electrostatic suction cup 2; or may only cover the surface of the control sheet 6 away from the electrostatic suction cup 2; or may simultaneously cover the surface of the control sheet 6 facing and away from the electrostatic suction cup 2, that is, cover the upper and lower surfaces of the control sheet 6.

[0051] In the above scheme, the position of the oxide film layer is not limited, as long as the oxide film layer covers at least one side surface of the control sheet 6 and covers the upper surface of the electrostatic chuck 2 through the control sheet 6 to protect the upper surface of the electrostatic chuck 2.

[0052] In some embodiments, the control wafer containing the oxide film layer can be reused.

[0053] In some embodiments, the cleaning gas 7 is sulfur hexafluoride (SF 6 ).

[0054] In some embodiments, the cleaning gas 7 includes sulfur hexafluoride (SF 6 ) and chlorine (Cl 2 ), in the process of forming plasma, the gas introduced into the process chamber 1 is SF 6 Before the cleaning process is about to end, a certain amount of Cl 2 The interior of the process chamber 1 and the surfaces of the control plate 6 and the electrostatic chuck 2 are cleaned.

[0055] In some other embodiments, the cleaning gas 7 is chlorine (Cl 2).

[0056] In some embodiments, the control sheet 6 is circular in shape, and the diameter of the control sheet is not less than the diameter of the electrostatic chuck.

[0057] It should be noted that the shape of the control sheet 6 is not limited to a circle, and can also be a deformed or irregular shape, as long as the control sheet 6 can cover the upper surface of the electrostatic chuck 2 and ensure that the oxide film layer thereon can cover the upper surface of the electrostatic chuck 2.

[0058] In some embodiments, the frequency of radio frequency excitation is 13.56 MHz or 27 Mhz.

[0059] In the above scheme, the frequency of radio frequency excitation is the common 13.56 MHz or 27 MHz, which is the frequency that radio frequency equipment is usually equipped with, which is conducive to promoting the above cleaning method.

[0060] In some embodiments, the wafer electrostatic chuck cleaning method is used to remove tungsten disulfide, that is, to remove tungsten disulfide formed as a byproduct in a tungsten etching process.

[0061] In the above scheme, the non-volatile tungsten disulfide is converted into gas under the action of plasma and conveniently discharged from the process chamber 1, so that the cleaning effect is good, the subsequent tungsten etching is guaranteed, downtime is prevented, and the yield of wafer etching is improved.

[0062] In some embodiments, after 75 to 125 tungsten etchings, the steps of any of the above schemes can be used to clean the electrostatic chuck 2. By regularly cleaning the electrostatic chuck 2, the continuity of the etching operation can be ensured, and the cleanliness of the electrostatic chuck 2 during the operation process can also be ensured.

[0063] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0064] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for cleaning an electrostatic chuck for a wafer, characterized in that: The following steps are involved: Covering the electrostatic chuck with a control sheet containing an oxide film layer; Under the condition that a direct current voltage and a cooling gas are not supplied to the electrostatic chuck, a cleaning gas injected into the process chamber is excited by radio frequency to generate plasma, wherein the plasma is used to convert the metal deposit on the electrostatic chuck into a gaseous state; discharging gaseous metal deposits from the process chamber; The control sheet is kept placed on the electrostatic chuck, and there is a gap between the control sheet and the electrostatic chuck, and the oxide film layer shields the upper surface of the electrostatic chuck through the control sheet to prevent the plasma from bombarding the upper surface of the electrostatic chuck; Before covering the control sheet on the electrostatic chuck, the cleaning method for the electrostatic chuck for the wafer further includes: evacuating the process chamber; The duration of radio frequency excitation of the cleaning gas is 20 to 30 seconds.

2. The cleaning method of the electrostatic chuck for wafer according to claim 1, characterized in that: The oxide film layer covers a surface of the control sheet facing toward and / or away from the electrostatic chuck.

3. The cleaning method of the electrostatic chuck for wafer according to claim 1, characterized in that: The cleaning gas includes at least one of sulfur hexafluoride and chlorine.

4. The cleaning method of the electrostatic chuck for wafer according to claim 1, characterized in that: The control plate is circular, and the diameter of the control plate is not less than the diameter of the electrostatic chuck.

5. The cleaning method of the electrostatic chuck for wafer according to claim 1, characterized in that: The frequency of the radio frequency excitation is 13.56 MHz or 27 MHz.

6. The cleaning method of the electrostatic chuck for wafer according to claim 1, characterized in that: The metal deposit includes tungsten disulfide.

7. The cleaning method of the electrostatic chuck for a wafer according to claim 6, characterized in that: After 75 to 125 tungsten etchings, the electrostatic chuck is cleaned.

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