Patent Publication Number: US-2023143115-A1

Title: Preventive Maintenance Method for Chamber of Metal Etching Machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority to Chinese Patent Application No. 202111319327.1, filed on Nov. 9, 2021, the disclosure of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present application relates to a semiconductor dry etching technology, in particular to a preventive maintenance method for a chamber of a metal etching machine. 
     BACKGROUND 
     Driven by Moore&#39;s law, with the gradual reduction of semiconductor process size, many new processes have been derived for the stability of device performance and the needs of process. Taking the Back Side Illumination (BSI) process as an example, in order to improve the process window in the lead loop, a W etchback dry etching process is developed, which has the advantage of stabilizing the monitoring parameters such as tungsten plug morphology and critical dimension. 
     The development of this kind of metal etching process has brought new challenges to the daily maintenance of equipment, especially the Preventive Maintenance (PM) of the etching chamber of the metal etching machine. The current PM process is as illustrated in  FIG.  1   : after the chamber enters the Mean Time Between Clean (MTBC) cycle, the equipment engineer opens the chamber for PM. For the sake of the clean room environment TVOC (Total Volatile Organic Compounds) monitoring and other considerations, DI water is required to be used to treat the chamber. At present, organic solvents are no longer allowed to be used for cleaning and maintenance, the removal effect of metal particles remaining on the surface of the ElectroStatic Chuck (ESC) and the chamber wall is poor. It is observed that there are particles that are difficult to remove on the surface of the ESC, as illustrated in  FIG.  2   . EDX (Energy Dispersive X-Ray Spectroscopy) analysis found that it contains metal components W/Al and the like, so there is the problem of metal particle residues. 
     After the PM of the metal etching chamber, the metal particles on the surface of the ESC will cause abnormal flow of backside helium on the wafer, which has a certain probability of abnormal downtime of backside helium in the PM recovery season. Such problems increase the uncertainty of the recovery of the chamber of the metal etching machine, hinder the online product tape-out, and cause the loss of production capacity, human, material and financial resources to the wafer factory. Therefore, solutions need to be found. 
     BRIEF SUMMARY 
     The technical problem to be solved by the present application is to provide a preventive maintenance method for a chamber of a metal etching machine. Before the chamber is opened for preventive maintenance, the phenomenon of metal particles remaining on the surface of the electrostatic chuck can be significantly improved, thus solving the downtime problem caused by abnormal backside helium. 
     In order to solve the technical problem, the preventive maintenance method for the chamber of the metal etching machine provided by the present application includes the following steps: 
     S 0 : the chamber of the metal etching machine entering mean time between clean; 
     S 1 : before the etching chamber of the metal etching machine is opened, cleaning an electrostatic chuck in the chamber and a chamber wall by using an O 2  burning cleaning method; 
     S 2 : exhausting and pumping down the chamber; 
     S 3 : cleaning the electrostatic chuck in the chamber and the chamber wall by using an NF 3 /Cl 2  burning cleaning method; 
     S 4 : exhausting and pumping down the chamber; 
     S 5 : opening the etching chamber of the metal etching machine for preventative maintenance. 
     Further, after step S 5 , step S 6  of cleaning the electrostatic chuck in the chamber and the chamber wall by using the O 2  burning cleaning method is performed. 
     Further, when the chamber is pumped down from an exhaust port, the opening of an exhaust valve at the exhaust port of the chamber is maximized. 
     Further, step S 1  includes the following steps: 
     S 11 : injecting O 2  from a gas inlet into the chamber at a flow greater than a first flow to clean the electrostatic chuck in a mode that the internal pressure of the chamber is lower than a first pressure by using the O 2  burning cleaning method; 
     S 12 : keeping the flow of O 2  injected form the gas inlet into the chamber unchanged to clean the electrostatic chuck and the chamber wall in a mode that the internal pressure of the chamber is higher than a second pressure by using the O 2  burning cleaning method, the second pressure being higher than the first pressure. 
     Further, the first pressure is 8.6 mt/m 2 ; 
     the second pressure is 43 mt/m 2 ; 
     the first flow is 200 sccm. 
     Further, step S 3  includes the following steps: 
     S 31 : injecting NF 3  from the gas inlet into the chamber at a flow greater than a second flow, injecting Cl 2  at a flow greater than a third flow and injecting SF 6  at a flow smaller than a fourth flow to clean the electrostatic chuck in the mode that the internal pressure of the chamber is lower than the first pressure by adopting the NF 3 /Cl 2  burning cleaning method, the second flow being greater than the third flow greater than the fourth flow; 
     S 32 : keeping the flow of NF 3 , Cl 2  and SF 6  injected form the gas inlet into the chamber unchanged, simultaneously injecting O 2  from the gas inlet into the chamber at a flow smaller than a fifth flow and injecting H 2  at a flow smaller than a sixth flow to clean the electrostatic chuck and the chamber wall in the mode that the internal pressure of the chamber is higher than the second pressure by using the NF 3 /Cl 2  burning cleaning method, the second flow being greater than the fifth flow greater than the sixth flow. 
     Further, the second flow is equal to the first flow. 
     Further, the second flow is 200 sccm, the third flow is 50 sccm, the fourth flow is 10 sccm, the fifth flow is 50 sccm and the sixth flow is 20 sccm. 
     In the preventative maintenance method for the chamber of the metal etching machine provided by the present application, an optimized burning cleaning recipe is added before the chamber is opened, and metal substances remaining on the surface of the ElectroStatic Chuck (ESC) are removed by adopting a cleaning/pumping down multi-step alternate method. Before the chamber is opened for Preventive Maintenance (PM), the phenomenon of metal particles remaining on the surface of the ESC can be significantly improved, thus solving the downtime problem caused by abnormal backside helium and ensuring the stability of mass production. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly describe the technical solution of the present application, the drawings required for the present application will be briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of the present application. Those skilled in the art may obtain other drawings based on these drawings without contributing any inventive labor. 
         FIG.  1    illustrates a schematic diagram of a recovery process of existing preventative maintenance. 
         FIG.  2    illustrates a schematic diagram of particles remaining on a surface of an electrostatic chuck in existing preventative maintenance. 
         FIG.  3    illustrates a flowchart of a preventive maintenance method for a chamber of a metal etching machine according to an embodiment of the present application. 
         FIG.  4    illustrates a schematic diagram of an improved situation of particles remaining on a surface of an electrostatic chuck in a preventive maintenance method for a chamber of a metal etching machine according to an embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION 
     The technical solution of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all of them. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without contributing any inventive labor still fall within the scope of protection of the present application. 
     Embodiment 1 
     Referring to  FIG.  3   , a Preventive Maintenance (PM) method for a chamber of a metal etching machine, which includes the following steps: 
     S 0 : the chamber of the metal etching machine entering Mean Time Between Clean (MTBC); 
     S 1 : before the etching chamber of the metal etching machine is opened, cleaning an ElectroStatic Chuck (ESC) in the chamber and a chamber wall by using an O 2  burning cleaning method; 
     S 2 : exhausting and pumping down the chamber to remove organic polymers in the chamber; 
     S 3 : cleaning the ESC in the chamber and the chamber wall by using an NF 3 /Cl 2  burning cleaning method; 
     S 4 : exhausting and pumping down the chamber to remove metal polymers in the chamber; 
     S 5 : opening the etching chamber of the metal etching machine for PM. 
     Further, after step S 5 , step S 6  of cleaning the ESC in the chamber and the chamber wall by using the O 2  burning cleaning method is performed. 
     Further, when the chamber is pumped down from an exhaust port, the opening of an exhaust valve at the exhaust port of the chamber is maximized. 
     In the preventative maintenance method for the chamber of the metal etching machine according to embodiment 1, an optimized burning cleaning recipe is added before the chamber is opened, and metal substances (such as WxFy/AlxFy) remaining on the surface of the ESC are removed by adopting a cleaning/pumping down multi-step alternate method. As illustrated in  FIG.  4   , before the chamber is opened for PM, the phenomenon of metal particles remaining on the surface of the ESC can be significantly improved, thus solving the downtime problem caused by abnormal backside helium and ensuring the stability of mass production. This method is applicable to the field of dry etching process technology of all semiconductor factories. 
     Embodiment 2 
     Based on the preventive maintenance method for the chamber of the metal etching machine according to embodiment 1, step S 1  includes the following steps: 
     S 11 : injecting O 2  from a gas inlet into the chamber at a flow greater than a first flow to clean the ESC in a mode that the internal pressure of the chamber is lower than a first pressure by using the O 2  burning cleaning method; 
     S 12 : keeping the flow of O 2  injected form the gas inlet into the chamber unchanged to clean the ESC and the chamber wall in a mode that the internal pressure of the chamber is higher than a second pressure by using the O 2  burning cleaning method, the second pressure being higher than the first pressure. 
     Further, the first pressure is 8.6 mt/m 2 ; the second pressure is 43 mt/m 2 ; the first flow is 200 sccm. 
     Embodiment 3 
     Based on the preventive maintenance method for the chamber of the metal etching machine according to embodiment 2, step S 3  includes the following steps: 
     S 31 : injecting NF 3  from the gas inlet into the chamber at a flow greater than a second flow, injecting Cl 2  at a flow greater than a third flow and injecting SF 6  at a flow smaller than a fourth flow to clean the ESC in the mode that the internal pressure of the chamber is lower than the first pressure by adopting the NF 3 /Cl 2  burning cleaning method, the second flow being greater than the third flow greater than the fourth flow; 
     S 32 : keeping the flow of NF 3 , Cl 2  and SF 6  injected form the gas inlet into the chamber unchanged, simultaneously injecting O 2  from the gas inlet into the chamber at a flow smaller than a fifth flow and injecting H 2  at a flow smaller than a sixth flow to clean the ESC and the chamber wall in the mode that the internal pressure of the chamber is higher than the second pressure by using the NF 3 /Cl 2  burning cleaning method, the second flow being greater than the fifth flow greater than the sixth flow. 
     Further, the second flow is equal to the first flow. 
     Further, the second flow is 200 sccm, the third flow is 50 sccm, the fourth flow is 10 sccm, the fifth flow is 50 sccm and the sixth flow is 20 sccm. 
     In the preventative maintenance method for the chamber of the metal etching machine according to embodiment 3, when using the NF 3 /Cl 2  burning cleaning method for ESC cleaning and chamber wall cleaning in the chamber, firstly NF 3 , Cl 2  and SF 6  are injected in the low pressure mode for ESC cleaning, then the flow of NF 3 , Cl 2  and SF 6  are kept unchanged, a small amount of O 2  and H 2  are added, and then the mode is switched to the high pressure mode for chamber wall cleaning. Not only the cleaning effect is good, but also the chamber can be protected. 
     What are described above are only preferred embodiments of the present application, which, however, are not used to limit the present application. Any modification, equivalent replacement, improvement and the like made within the essence and principle of the present application shall be included in the scope of protection of the present application.