Patent Publication Number: US-2023132759-A1

Title: Method of manufacturing vias with pulsing plasma

Description:
BACKGROUND 
     Field of Disclosure 
     The present disclosure relates to a method of manufacturing vias with pulsing plasma. 
     Description of Related Art 
     Semiconductor industries are developing and improving the manufacturing process for semiconductor structures, while the miniature of the components continued. The accuracy of the scale and shape of the structure thus become more important. To create vias in a semiconductor structure, reaction ion etching methods are often used. The species of the ion particles are decided by the compounds of the plasma, which needs to consider the selective etching rate of the species of the ion particles between different materials. Suitable prescription for the etching process is necessary and indispensable. 
     SUMMARY 
     The disclosure provides a method of manufacturing vias with pulsing plasma. 
     According to an embodiment of the present disclosure, a method of manufacturing a semiconductor, comprising: providing a stacked structure comprising a first oxide layer, a second oxide layer, and a metal layer stacked between the first oxide layer and the second oxide layer; forming a mask layer on the second oxide layer; introducing a gas mixture to the stacked structure, wherein the gas mixture includes at least two hydrocarbon compounds and oxygen; and performing a pulsing plasma process to the stacked structure through the mask layer to pattern the second oxide layer and expose the metal layer through the patterned second oxide layer. 
     In an embodiment of the present disclosure, the forming the mask layer includes: forming a first covering layer on the second oxide layer; and patterning the first covering layer to expose at least one portion of a surface of the second oxide layer. 
     In an embodiment of the present disclosure, method further comprising: forming a second covering layer on the patterned first covering layer to cover and contact the at least one portion of the surface of the second oxide layer. 
     In an embodiment of the present disclosure, the forming the second covering layer is performed by using a blanket deposition process. 
     In an embodiment of the present disclosure, the second covering layer includes a high dielectric material. 
     In an embodiment of the present disclosure, the first covering layer includes zirconium oxide or hafnium oxide. 
     In an embodiment of the present disclosure, the method further comprising: forming another mask layer on the patterned second oxide layer; and performing another pulsing plasma process to the stacked structure through the another mask layer to form at least one via running through the first oxide layer, the metal layer, and the second oxide layer. 
     In an embodiment of the present disclosure, the forming the another mask layer includes: forming a first covering layer on the patterned second oxide layer; and forming a second covering layer on the another first covering layer to cover and contact at least one portion of a surface of the metal layer. 
     In an embodiment of the present disclosure, the forming the second covering layer is performed by using a blanket deposition process. 
     In an embodiment of the present disclosure, the second covering layer includes a high dielectric material. 
     In an embodiment of the present disclosure, the first covering layer includes zirconium oxide or hafnium oxide. 
     In an embodiment of the present disclosure, the performing the pulsing plasma process further form at least one via running through the first oxide layer, the metal layer, and the second oxide layer. 
     In an embodiment of the present disclosure, the at least two hydrocarbon compounds include a saturated hydrocarbon compound and an unsaturated hydrocarbon compound or include two unsaturated hydrocarbon compounds. 
     In an embodiment of the present disclosure, one of the at least two hydrocarbon compounds has an additional double bond comparing to another one of the at least two hydrocarbon compounds. 
     In an embodiment of the present disclosure, the metal layer includes tungsten. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG.  1    is a flow chart of the method of manufacturing vias with pulsing plasma according to one embodiment of this disclosure. 
         FIG.  2 A  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure; 
         FIG.  2 B  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure; 
         FIG.  2 C  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure; 
         FIG.  2 D  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure; 
         FIG.  2 E  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure; and 
         FIG.  3    is an enlarge view of  FIG.  2 D  according to one embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Reference is made to  FIG.  1   .  FIG.  1    is a flow chart of a method M 1  of manufacturing vias with pulsing plasma according to one embodiment of this disclosure. As shown in  FIG.  1   , the method M 1  of manufacturing vias with pulsing plasma includes: providing a stacked structure including a first oxide layer, a second oxide layer, and a metal layer stacked between the first oxide layer and the second oxide layer (step S 110 ); forming a mask layer on the second oxide layer (step S 120 ); introducing a gas mixture to the stacked structure, wherein the gas mixture includes at least two hydrocarbon compounds and oxygen (step S 130 ); and performing a pulsing plasma process to the stacked structure through the mask layer to pattern the second oxide layer and expose the metal layer through the patterned second oxide layer (step S 140 ). 
     References are made to  FIG.  2 A  and  FIG.  1   .  FIG.  2 A  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure. As shown in  FIG.  2 A  and  FIG.  1   , a stacked structure  110  is provided in step S 110 . The stacked structure  110  is formed by sequentially stacking a first oxide layer  112 , a metal layer  114 , and a second oxide layer  116 . In an embodiment, the metal layer  114  includes tungsten. In practical applications, the metal layer  114  may include other metal. In some embodiments, the thickness of the metal layer  114  may be about 80 nm. In some embodiments, the thickness ratio of the first oxide layer  112 , the metal layer  114 , and the second oxide layer  116  is 2:1:1. However, any suitable thickness of the first oxide layer  112 , the metal layer  114  and the second oxide layer  116  may be utilized. 
     References are made to  FIG.  2 B  and  FIG.  1   .  FIG.  2 B  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure. As shown in  FIG.  2 B  and  FIG.  1   , a mask layer  120  is provided in step S 120 . The mask layer  120  may include multiple sublayers, and different sublayers may be formed by using different processes. In an embodiment, step S 120  includes: forming a first covering layer on the second oxide layer (step S 121 ); and patterning the first covering layer to expose at least one portion of a surface of the second oxide layer (step S 122 ). Specifically, in step S 121 , the first covering layer  122  may be deposited over the second oxide layer  116  by using any suitable deposition process, such as chemical vapor deposition, physical vapor deposition, the combination of thereof, or the likes. In an embodiment, the first covering layer  122  includes zirconium oxide or hafnium oxide, but the preset disclosure is not limited to this. After the deposition of the first covering layer  122 , step S 122  is performed in order to pattern the first covering layer  122 . The first covering layer  122  may be patterned by using, such as a photolithography process, but the present disclosure is not limited to this. Reference is made to  FIG.  2 B . In an embodiment, after the first covering layer  122  is patterned, the patterned first covering layer  122  will expose some portions of the top surface of the second oxide layer  116 . The portions which are unexposed by the patterned first covering layer  122  may be protected by the patterned first covering layer  122  until the patterned first covering layer  122  is fully removed. 
     Reference is made to  FIG.  2 B . Step S 120  further includes: forming a second covering layer on the patterned first covering layer to cover and contact the at least one portion of the surface of the second oxide layer (step S 123 ). In an embodiment, the mask layer  120  includes a first covering layer  122  and a second covering layer  124 , but the present disclosure is not limited to this. Any suitable number of the sublayers of the mask layer  120  may be utilized. In an embodiment, step S 123  is performed by using a blanket deposition process. The second covering layer  124  is conformally formed over the second oxide layer  116  and the first covering layer  122 . Specifically, in  FIG.  2 B , the second covering layer  124  contacts with some portions of the top surface of the second oxide layer  116  and the top surface and the sidewalls of the patterned first covering layer  122 , but the present disclosure is not limited to this. The second covering layer  124  may help to reduce the side etching of the vias during the following pulsing plasma process, and thus enhance the straightness of the side walls of the vias. For example, in step S 123 , the second covering layer  124  is deposited by using, such as an atomic layer deposition process. In an embodiment, the second covering layer  124  includes a high dielectric material, but the preset disclosure is not limited to this. The thickness of the mask layer  120  (including the thickness of the first covering layer  122  and the thickness of the second covering layer  124 ) may be about 180 nm. However, any suitable thickness of the second covering layer  124  may be utilized. 
     Reference is made to  FIG.  2 C .  FIG.  2 C  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure. As shown in  FIG.  2 C  and  FIG.  1   , after forming the second covering layer  124 , a gas mixture is introduced in step S 130 . The gas mixture is used for producing plasma with specific element and ion compounds, which may provide a suitable selective etching rate between the stacked structure  110  and the mask layer  120 . The compounds of the gas mixture that is used for the following pulsing plasma process may mainly be decided by the etching rates thereof to the materials of the metal layer  114 , the first covering layer  122 , and the second covering layer  124 . The gas mixture includes at least two hydrocarbon (C x F y ) compounds and oxygen to provide a suitable selective etching rate between the metal layer  114  and the mask layer  120  (which includes the first covering layer  122  and the second covering layer  124 ). 
     Specifically, in an embodiment, the at least two hydrocarbon compounds include a saturated hydrocarbon compound and an unsaturated hydrocarbon compound or include two unsaturated hydrocarbon compounds. For example, the saturated hydrocarbon compound may be such as CF 4 , or the likes, and the unsaturated hydrocarbon compound may be such as C 4 F 6 , C 4 F 8 , or the likes, but the present disclosure is not limited to this. Any suitable hydrocarbon compound that satisfies the definition of saturated or unsaturated may be utilized. The at least two hydrocarbon compounds thus may be selected from the above gases, such as CF 4  and C 4 F 6 , which is an example for the gas mixture with the combination of a saturated hydrocarbon compound and an unsaturated hydrocarbon compound, or possibly, a gas mixture including C 4 F 6  and C 4 F 8  provides an example for the case in which the gas mixture includes two unsaturated hydrocarbon compounds. The ratio between the two or more compounds of the gas mixture may be decided according to the selective etching rate between the materials of the mask layer  120  and the stacked structure  110 , but any suitable compounds ratio may be utilized. In another embodiment, one of the at least two hydrocarbon compounds has an additional double bond comparing to another one of the at least two hydrocarbon compounds. For example, in an embodiment, the compound of the gas mixture may include C 4 F 8  and C 5 F 8 , in which C 4 F 8  includes four single bonds between the carbon elements, while C 5 F 8  includes four single bonds and one double bond between the carbon elements. However, any suitable hydrocarbon compound that satisfies the relation may be utilized. 
     References are made to  FIG.  2 C  and  FIG.  1   . After the gas mixture is introduced, the pulsing plasma process is performed in step S 140 . An electric field is applied to the stacked structure  110 , which may attract the ion particles of the plasma moving along a direction and collide with the stacked structure  110 . The electric field may be provided by applying a bias between two electrically separated electrodes. The electric intensity of the electric field may be controlled by adjusting the bias which is applied on the electrodes. For example, pulsing biases applied on the electrodes may create pulsing electric field utilized in the pulsing plasma process. The bias power may be about 4000 W, but the present disclosure is not limited to this. Any suitable bias power may be utilized. While the electric field is applied, the ion particles of the plasma will collide with the stacked structure  110 . More specifically, the ion particles will collide with the mask layer  120  and the portions of the second oxide layer  116  which are exposed by the mask layer  120 . Taking tungsten as the material of the metal layer  114  for example, during applying electric field, the collision between the tungsten and the ion particles produces highly volatile reactants, such as WF 6 , or the likes, which will be pumped out by a gas pump. One of the reasons for choosing pulsing plasma to etch the stacked structure  110  is to better control the etching process by reducing any uncontrollable particles (such as reactant particles) that will leads to unwanted etching profile. 
     Reference is made to  FIG.  2 D .  FIG.  2 D  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure. As shown in  FIG.  2 D , the etching process of the method M 1  may include multiple pulsing plasma processes, and each pulsing plasma process may aim to etch different layers of the stacked structure  110 , but the present disclosure is not limited to this. For example, in an embodiment, the method M 1  further includes: forming another mask layer on the patterned second oxide layer (step S 150 ); and performing another pulsing plasma process to the stacked structure through the another mask layer to form at least one via running through the first oxide layer, the metal layer, and the second oxide layer (step S 160 ). The reason to perform multiple steps of pulsing plasma is to develop a suitable prescription of the gas mixture and the parameters that are used during the pulsing plasma process for providing vias with highly straightness sidewalls, but the present disclosure is not limited to this. 
     Specifically, after the second oxide layer  116  is etched by the first pulsing plasma process as shown in  FIG.  2 C , another mask layer  130  is formed over the patterned second oxide layer  116 . In an embodiment, step S 150  includes: forming another first covering layer on the patterned second oxide layer (step S 151 ); and forming another second covering layer on the another first covering layer to cover and contact at least one portion of a surface of the metal layer (step S 152 ). For example, the another mask layer  130  may also include multiple sublayers, such as the another first covering layer  132  and the another second covering layer  134  which are shown in  FIG.  2 D . The formation of the another first covering layer  132  and the another second covering layer  134  may be similar or the same as the formation of the first covering layer  122  and the second covering layer  124  described above, but the present disclosure is not limited to this. Any suitable process may be utilized. Additionally, the materials and the thicknesses of the another first covering layer  132  and the another second covering layer  134  may be similar or the same as those of the first covering layer  122  and the second covering layer  124  described above. For example, in an embodiment, the another first covering layer  132  includes zirconium oxide or hafnium oxide. However, any suitable materials and thicknesses may be utilized. 
     References are made to  FIG.  2 D  and  FIG.  3   .  FIG.  3    is an enlarge view of  FIG.  2 D  according to one embodiment of this disclosure. As shown in  FIG.  2 D  and  FIG.  3   , the another mask layer  130  is formed over the stacked structure  110 . Specifically, in an embodiment, the another second covering layer  134  is performed by using a blanket deposition process. The another second covering layer  134  is conformally formed over the second oxide layer  116  and the another first covering layer  132 . Specifically, in  FIG.  2 D , the another second covering layer  134  contacts with some portions of the top surface of the metal layer  114  and the top surface and the sidewalls of the another first covering layer  132  and the second oxide layer  116 , but the present disclosure is not limited to this. The another second covering layer  134  may help to reduce the side etching during the following pulsing plasma process, and thus enhance the straightness of the side walls of the vias. For example, the another second covering layer  134  is deposited by using, such as an atomic layer deposition process. In an embodiment, the another second covering layer  134  includes a high dielectric material, but the preset disclosure is not limited to this. 
     Specifically, in  FIG.  3   , the left sidewall and the right side wall of the opening  140  are defined by the first side wall  142  and the second side wall  144  respectively, and the bottom wall  146  of the opening  140  is defined by the top surface of the metal layer  114  which is exposed by the another first covering layer  132  and the second oxide layer  116 . The top surface of the another first covering layer  132 , the first side wall  142 , the second side wall  144 , and the bottom wall  146  are covered by the another second covering layer  134 . The another first covering layer  132  and the another second covering layer  134  protect the patterned second oxide layer  116  and portions of the metal layer  114  and the first oxide layer  112  beneath. The adopted pulsing plasma process may be an anisotropic etching process, which may has higher etching rate along one certain direction (such as a first direction A 1 ), while has less etching rate in other directions (such as a second direction A 2 ). During the pulsing plasma process, surface etching is achieved by the collisions between the ion particles and the surface of the stacked structure  110 . In the embodiment as shown in  FIG.  3   , the first direction A 1  may be perpendicular to the top surface of the another first covering layer  132  and the bottom wall  146 , while the second direction A 2  may be perpendicular to the first side wall  142  and the second side wall  144 . The portions of the stacked structure  110  which are covered by the mask layer  130  may be retained after the etching process. However, the portions exposed by the opening  140  are only protected by the another second covering layer  134  and may be etched more or less during the procedure. The another second covering layer  134  can protect the first side wall  142  and the second side wall  144  from side etching, thus to improve the straightness of the side walls, while letting the ion particles to collide with the bottom wall  146  and extend the opening  140  through the metal layer  114  and the first oxide layer  112 . The top surface of the second oxide layer  116  is protected by the another first covering layer  132  and the another second covering layer  134 , and thus will be retained after the etching process. 
     Reference is made to  FIG.  2 E .  FIG.  2 E  is a schematic diagram showing an intermediate stage of the method according to one embodiment of this disclosure. As shown in  FIG.  2 E , after finishing multiple pulsing plasma processes, vias  150  that penetrate through the stacked structure  110  are formed. In an embodiment, step S 160  further forms at least one via running through the first oxide layer  112 , the metal layer  114 , and the second oxide layer  116 . Further, after confirming the suitable prescription of the gas mixture and the parameters that are used during the pulsing plasma process, the multiple pulsing plasma processes may be simplified to one pulsing plasma process, and thus reduce the cost of manufacturing. The one-time execution of the pulsing plasma process may be similar to or the same as the pulsing plasma process described above. However, any suitable methods can be utilized. 
     Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.