Patent Publication Number: US-2023142968-A1

Title: Method for Manufacturing High-Voltage Metal Gate Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority to Chinese Patent Application No. 202111320661.9, 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 manufacturing technology, in particular to a method for manufacturing a high-voltage metal gate device. 
     BACKGROUND 
     From the node of 28 nm, the high-performance process will use HK (high dielectric constant) dielectric and metal gate to improve the performance of the device. Metal Chemical-Mechanical Polishing (CMP) process is inevitably used in the metal gate process. In the metal CMP process, large patterns will inevitably have the problem of dishing, so the size of the gate cannot be designed too large. However, for the high-voltage device (with operating voltage of 8V-40V), it is inevitable to need a relatively large gate size to undertake high-voltage operation, which will cause the decline or even loss of gate height in large metal gates. The process specifically includes the following steps: 
     1. After a pre-process, gate photolithography, etching and sidewall processes are performed to define at least one dummy poly gate, and at least one dummy poly gate is dummy poly high-voltage gate  2 , and dummy polycrystalline  3  of the dummy poly gate is formed on a gate dielectric layer  8 , as illustrated in  FIG.  1   . 
     2. Isolation dielectric  4  is filled between the dummy poly gates and a CMP process is performed, as illustrated in  FIG.  2   . 
     3. The dummy polycrystalline on the gate dielectric layer  8  of the dummy poly gate is removed through selective etching, as illustrated in  FIG.  3   . 
     4. A gate metal  5  is deposited on a wafer, as illustrated in  FIG.  4   . 
     5. Gate metal CMP is performed. Since the gate metal  5  on the high-voltage gate  2  is comparatively large, CMP dishing will be caused, resulting in that the middle of the gate metal  5  on the high-voltage gate  2  is thin or even empty, as illustrated in  FIG.  5   . 
     In order to solve this problem, the current common method is to add a trench in a large-area high-voltage gate. The specific process includes the following steps: 
     (1) During the lithography and etching of the dummy poly gate, a trench connected to the gate dielectric layer  8  is dug out through a mask in the middle of the large-area dummy polycrystalline  3  on the high-voltage gate  2 , as illustrated in  FIG.  6   . 
     (2) An isolation dielectric  4  is filled between the dummy poly gates and a CMP process is performed. 
     (3) The dummy polycrystalline  3  on the high-voltage gate  2  is removed through selective etching. 
     (4) A gate metal  5  is deposited on a wafer. 
     (5) A gate metal CMP process is performed. 
     In the method of adding a trench in the dummy polycrystalline  3  of the large-area high-voltage gate  2 , since the middle of the large-area dummy polycrystalline  3  of the high-voltage gate  2  is blocked by the isolation dielectric  4  filled in the trench, CMP dishing will not be caused. However, in the method of adding a trench in the large-area dummy polycrystalline  3  of the high-voltage gate  2 , as illustrated in  FIG.  6   , since the trench in the large-area dummy polycrystalline  3  of the high-voltage gate  2  exposes the gate dielectric layer  8  below, subsequent processes including ion implantation, metal silicide and the like will introduce ions into the gate dielectric layer  8 . At the same time, etching and acid pickling will also influence the exposed gate dielectric layer  8 , and the electrical properties of the high-voltage device will be affected, causing the electrical properties of the high-voltage device to shift under high voltage and high temperature, and reducing the reliability of the high-voltage device. 
     BRIEF SUMMARY 
     The technical problem to be solved by the present application is to provide a method for manufacturing a high-voltage metal gate device, which not only avoids the dishing problem of the large gate metal, but also can avoid affecting the electrical properties of the high-voltage device due to the influence on the gate dielectric layer. 
     In order to solve the above technical problem, the method for manufacturing the high-voltage metal gate device provided by the present application includes the following steps: 
     S 1 : after a pre-process, performing gate photolithography, etching and sidewall processes to define at least one dummy poly gate, and at least one dummy poly gate is dummy poly high-voltage gate  2 , and dummy polycrystalline  3  of the dummy poly gate being formed on a gate dielectric layer  8 . 
     S 2 : filling isolation dielectric  4  between the dummy poly gates and performing a CMP process; 
     S 3 : removing the dummy polycrystalline on the gate dielectric layer  8  of the dummy poly gate through selective etching; 
     S 4 : depositing a gate metal  5  on a wafer; 
     S 5 : performing a gate metal CMP process to reduce the thickness of the gate metal  5  deposited on the wafer; 
     S 6 : depositing a blocking dielectric layer  6  on the gate metal  5 ; 
     S 7 : opening a high-voltage gate  2  region through photolithography, and removing the blocking dielectric layer  6  outside the high-voltage gate  2  region through etching; 
     S 8 : performing a gate metal CMP process to reduce the thickness of the gate metal  5  deposited on the wafer, wherein due to the blocking effect of the blocking dielectric layer  6 , the gate metal  5  in the high-voltage gate  2  region is higher than the gate metal  5  outside the high-voltage gate  2  region; 
     S 9 : removing the blocking dielectric layer  6  on the gate metal  5  in the high-voltage gate  2  region through dry etching or acid pickling. 
     Further, after step S 9 , the method for manufacturing the high-voltage metal gate device further includes step S 10 : performing a gate metal CMP process to adjust the height of the gate metal  5 . 
     Further, in step S 8 , the gate metal CMP process is performed to remove the gate metal  5  above the isolation dielectric  4  outside the high-voltage gate  2  region, wherein due to the blocking effect of the blocking dielectric layer  6 , the gate metal  5  in the high-voltage gate  2  region is higher than the blocking dielectric layer  6 . 
     Further, in step S 1 , the defined dummy poly gate includes at least one dummy polycrystalline high-voltage gate  2  and one dummy polycrystalline low-voltage gate  1 . 
     Further, the length of the high-voltage gate  2  is greater than 2.5 μm. 
     Further, in step S 4 , the thickness of the gate metal  5  deposited on the wafer is greater than the thickness of the isolation dielectric  4  between gates after step S 2 . 
     Further, in step S 4 , the thickness of the gate metal  5  deposited on the wafer is 30 nm-200 nm. 
     Further, in step S 5 , the gate metal CMP process is performed to reduce the thickness of the gate metal  5  deposited on the wafer, and the lowest position of an upper surface of the gate metal  5  is higher than the isolation dielectric  4  between gates. 
     Further, in S 5 , the gate metal CMP process is performed to reduce the thickness of the gate metal  5  deposited on the wafer by 1/3-2/3. 
     Further, the gate dielectric layer  8  is SiON, HfO 2  or SiO 2 , 
     the isolation dielectric  4  is SiN or SiO 2 , 
     the blocking dielectric layer  6  is SiN or SiO 2 , 
     the gate metal  5  is Al, Ti or W. 
     In the method for manufacturing the high-voltage metal gate device provided by the present application, after the deposition of a gate metal  5  through a normal process, in CMP processes performed to the gate metal  5 , firstly a first CMP process is performed to thin the gate metal  5  to a certain thickness in advance, then a blocking dielectric layer  6  is deposited, a large-area high-voltage gate  2  region is opened through photolithography, and the blocking dielectric layer  6  other than the blocking dielectric layer in the large-area high-voltage gate  2  region is removed through etching. In a second CMP process performed to the gate metal  5 , due to the blocking dielectric layer on the surface of the large-area gate metal  5  in the high-voltage gate  2  region, the polishing speed is slow, and CMP dishing will not be caused. The method for manufacturing the high-voltage metal gate device not only avoids the dishing problem of the large gate metal, but also can avoid affecting the electrical properties of the high-voltage device due to the influence on the gate dielectric layer  8 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to more clearly describe the technical solution of the present application, the following will briefly introduce the drawings needed in the present application. It is obvious that the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without contributing any inventive labor. 
         FIG.  1    illustrates a schematic diagram of a dummy poly gate defined by adopting a method for manufacturing a high-voltage metal gate device. 
         FIG.  2    illustrates a schematic diagram after filling an isolation dielectric between dummy poly gates in a method for manufacturing a high-voltage metal gate device. 
         FIG.  3    illustrates a schematic diagram after removing dummy polycrystalline in a method for manufacturing a high-voltage metal gate device. 
         FIG.  4    illustrates a schematic diagram after depositing a gate metal in a method for manufacturing a high-voltage metal gate device. 
         FIG.  5    illustrates a schematic diagram of CMP dishing caused during gate metal CMP in an existing method for manufacturing a high-voltage metal gate device. 
         FIG.  6    illustrates a schematic diagram of a trench connected to a gate dielectric layer dug out through a mask in the middle of large-area dummy polycrystalline on a high-voltage gate. 
         FIG.  7    illustrates a schematic diagram after performing a gate metal CMP process to reduce the thickness of a gate metal for the first time in a method for manufacturing a high-voltage metal gate device according to an embodiment of the present application. 
         FIG.  8    illustrates a schematic diagram after depositing a blocking dielectric layer on a gate metal in a method for manufacturing a high-voltage metal gate device according to an embodiment of the present application. 
         FIG.  9    illustrates a schematic diagram after removing a blocking dielectric layer outside a high-voltage gate region in a method for manufacturing a high-voltage metal gate device according to an embodiment of the present application. 
         FIG.  10    illustrates a schematic diagram after performing a gate metal CMP process to reduce the thickness of a gate metal for the second time in a method for manufacturing a high-voltage metal gate device according to an embodiment of the present application. 
         FIG.  11    illustrates a schematic diagram after removing a blocking dielectric layer on a gate metal in a high-voltage gate region and performing slight polishing in a method for manufacturing a high-voltage metal gate device 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, instead of all of them. Based on the embodiments in 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 
     A method for manufacturing a high-voltage metal gate device includes the following steps: 
     S 1 : after a pre-process, performing gate photolithography, etching and sidewall processes to define at least one dummy poly gate, and at least one dummy poly gate is dummy poly high-voltage gate  2 , and dummy polycrystalline  3  of the dummy poly gate being formed on a gate dielectric layer  8 , as illustrated in  FIG.  1   . 
     S 2 : filling isolation dielectric  4  between the dummy poly gates and performing a CMP process, as illustrated in  FIG.  2   ; 
     S 3 : removing the dummy polycrystalline on the gate dielectric layer  8  of the dummy poly gate through selective etching, as illustrated in  FIG.  3   ; 
     S 4 : depositing a gate metal  5  on a wafer, as illustrated in  FIG.  4   ; 
     S 5 : performing a gate metal CMP process to reduce the thickness of the gate metal  5  deposited on the wafer, as illustrated in  FIG.  7   ; 
     S 6 : depositing a blocking dielectric layer  6  on the gate metal  5 , as illustrated in  FIG.  8   ; 
     S 7 : opening a high-voltage gate  2  region through photolithography, and removing the blocking dielectric layer  6  outside the high-voltage gate  2  region through etching, as illustrated in  FIG.  9   ; 
     S 8 : performing a gate metal CMP process to reduce the thickness of the gate metal  5  deposited on the wafer, wherein due to the blocking effect of the blocking dielectric layer  6 , the gate metal  5  in the high-voltage gate  2  region is higher than the gate metal  5  outside the high-voltage gate  2  region, as illustrated in  FIG.  10   ; 
     S 9 : removing the blocking dielectric layer  6  on the gate metal  5  in the high-voltage gate  2  region through dry etching or acid pickling. 
     Further, after step S 9 , the method for manufacturing the high-voltage metal gate device further includes step S 10 : performing a slight gate metal CMP process to adjust the height of the gate metal  5 , as illustrated in  FIG.  11   . 
     In the method for manufacturing the high-voltage metal gate device according to embodiment 1, after the deposition of a gate metal  5  through a normal process, in CMP processes performed to the gate metal  5 , firstly a first CMP process is performed to thin the gate metal  5  to a certain thickness in advance, then a blocking dielectric layer  6  is deposited, a large-area high-voltage gate  2  region is opened through photolithography, and the blocking dielectric layer  6  other than the blocking dielectric layer in the large-area high-voltage gate  2  region is removed through etching. In a second CMP process performed to the gate metal  5 , due to the blocking dielectric layer  6  on the surface of the large-area gate metal  5  in the high-voltage gate  2  region, the polishing speed is slow, and CMP dishing will not be caused. 
     The method for manufacturing the high-voltage metal gate device according to embodiment 1 not only avoids the dishing problem of the large gate metal, but also can avoid affecting the electrical properties of the high-voltage device due to the influence on the gate dielectric layer  8 . 
     Embodiment 2 
     Based on the method for manufacturing the high-voltage metal gate device according to embodiment 1, in step S 1 , the defined dummy poly gate includes at least one dummy polycrystalline high-voltage gate  2  and one dummy polycrystalline low-voltage gate  1 . 
     Further, the length of the high-voltage gate  2  is greater than 2.5 μm. 
     Embodiment 3 
     Based on the method for manufacturing the high-voltage metal gate device according to embodiment 1, in step S 8 , the gate metal CMP process is performed to remove the gate metal  5  above the isolation dielectric  4  outside the high-voltage gate  2  region. Due to the blocking effect of the blocking dielectric layer  6 , the gate metal  5  in the high-voltage gate  2  region is higher than the blocking dielectric layer  6 . 
     Embodiment 4 
     Based on the method for manufacturing the high-voltage metal gate device according to embodiment 1, in step S 4 , the thickness of the gate metal  5  deposited on the wafer is greater than the thickness of the isolation dielectric  4  between gates after step S 2 . 
     Further, in step S 4 , the thickness of the gate metal  5  deposited on the wafer is 30 nm-200 nm. 
     Embodiment 5 
     Based on the method for manufacturing the high-voltage metal gate device according to embodiment 1, in step S 5 , the gate metal CMP process is performed to reduce the thickness of the gate metal  5  deposited on the wafer, and the lowest position of an upper surface of the gate metal  5  is higher than the isolation dielectric  4  between gates. 
     Further, in S 5 , the gate metal CMP process is performed to reduce the thickness of the gate metal  5  deposited on the wafer by 1/3-2/3. 
     Further, the gate dielectric layer  8  is SiON, HfO 2  or SiO 2 , 
     Further, the isolation dielectric  4  is SiN or SiO 2 , 
     Further, the blocking dielectric layer  6  is SiN or SiO 2 , 
     Further, the gate metal  5  is Al, Ti or W. 
     What are described above are only preferred embodiments of the present application and are not used to limit the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.