Patent Publication Number: US-2022216086-A1

Title: Member for semiconductor manufacturing apparatus and method for manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a member for semiconductor manufacturing apparatus and method for manufacturing the same. 
     2. Description of the Related Art 
     Examples of member for semiconductor manufacturing apparatus known thus far include a member including an electrostatic chuck having a wafer placement surface on its upper surface. For example, a member for semiconductor manufacturing apparatus described in Patent Literature 1 includes a cooling plate disposed on an undersurface of an electrostatic chuck with an intermediate plate interposed therebetween. The cooling plate has a gas feed port. The electrostatic chuck has a gas outlet port that extends through from the undersurface to the wafer placement surface. The intermediate plate and the cooling plate define an opening continuous with the gas feed port and the gas outlet port. A closely packed plug is arranged in this opening. The closely packed plug has a gas flow path that extends through between the upper surface and the lower surface while winding. The member for semiconductor manufacturing apparatus processes a wafer placed on the wafer placement surface in a chamber with plasma caused by introducing a gas material in the chamber and applying a radio frequency (RF) voltage for causing plasma on the cooling plate. At this time, backside gas such as helium is introduced into the gas feed port. The backside gas is supplied to the back surface of the wafer from the gas feed port through the gas flow path in the closely packed plug and the gas outlet port. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: US 2017/0243726 A1 
       
    
     SUMMARY OF THE INVENTION 
     However, in Patent Literature 1, the closely packed plug is simply disposed in a space, and thus a gap may be left between the closely packed plug and the inner surface of the space. Even such a gap may cause dielectric breakdown, and thus is not preferable. Even if the closely packed plug is bonded to the space with a resin-made adhesive interposed therebetween to prevent a gap from being left, the adhesive may flow into the gas outlet port to block the gas outlet port. 
     The present invention is made to address such a problem, and aims to provide a structure where a gas outlet port is not blocked by an adhesive material that supports a plug. 
     A member for semiconductor manufacturing apparatus according to the present invention includes: a ceramic plate having a wafer placement surface and including a built-in electrode; a plug receiving hole formed in a surface of the ceramic plate opposite to the wafer placement surface; a gas outlet port that extends through a bottom wall of the plug receiving hole in the ceramic plate in a thickness direction of the ceramic plate; a plug received in the plug receiving hole; and a gas flow path disposed inside the plug to be continuous with the gas outlet port and allow gas flow in a thickness direction of the plug, wherein a stepped portion is disposed on a side surface of the plug or an inner surface of the plug receiving hole, the plug receiving hole and the plug are in contact with each other in an area deeper than the stepped portion, a gap is formed between the plug receiving hole and the plug in an area shallower than the stepped portion, and a plug support member made of an adhesive material is formed in the gap. 
     In this member for semiconductor manufacturing apparatus, the plug receiving hole and the plug are in contact with each other in the area deeper than the stepped portion disposed on the side surface of the plug or the inner surface of the plug receiving hole, the gap is formed between the plug receiving hole and the plug in the area shallower than the stepped portion, and the plug support member made of the adhesive material is formed in the gap. Regardless of when the adhesive is injected into the gap between the plug and the plug receiving hole to manufacture this member for semiconductor manufacturing apparatus, the adhesive is prevented from flowing into an area further beyond the stepped portion, and prevented from flowing into a gas outlet port. Thus, the gas outlet port is prevented from being blocked by the adhesive material supporting the plug, that is, a plug support member. 
     In the member for semiconductor manufacturing apparatus according to the present invention, the plug may include a first taper portion having a diameter gradually decreasing toward an opening of the plug receiving hole. In this structure, the plug support member receives the first taper portion of the plug from below, and thus prevents the plug from slipping out from the plug receiving hole. 
     In the member for semiconductor manufacturing apparatus according to the present invention, the plug may have a second taper portion having a diameter gradually decreasing toward a bottom surface of the plug receiving hole, an outer surface of the second taper portion may be in contact with an inner surface of the plug receiving hole, the electrode may be disposed in a plane inside the ceramic plate crossing the second taper portion, and may have a through-hole to allow the plug to pass therethrough. Thus, the plug including the second taper portion can further reduce the diameter of the through-hole than in the case of the plug not including the second taper portion. 
     In the member for semiconductor manufacturing apparatus according to the present invention, the plug may be made of a closely-packed ceramic material, and the gas flow path may be helical. This structure can prevent plasma from discharging via a gas flow path. 
     A method for manufacturing a member for semiconductor manufacturing apparatus according to the present invention is a method for manufacturing any one of the above-described member for semiconductor manufacturing apparatus, and includes (a) a step of preparing the ceramic plate and the plug, (b) a step of inserting the plug into the plug receiving hole to bring the plug into contact with the plug receiving hole in an area deeper than a stepped portion disposed on a side surface of the plug or an inner surface of the plug receiving hole and to form a gap between the plug receiving hole and the plug in an area shallower than the stepped portion, and (c) a step of injecting an adhesive into the gap and then curing the adhesive to form the plug support member. 
     With this method for manufacturing the member for semiconductor manufacturing apparatus, when the adhesive is filled into the gap, the adhesive is prevented from flowing further beyond the stepped portion. Thus, the adhesive is prevented from flowing into the gas outlet port. The gas outlet port is thus prevented from being blocked by the adhesive material supporting the plug, that is, the plug support member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical cross-sectional view of a member for semiconductor manufacturing apparatus  10 . 
         FIG. 2  is a plan view of a ceramic plate  20 . 
         FIG. 3  is an enlarged view of part of the member for semiconductor manufacturing apparatus  10  illustrated in  FIG. 1 . 
         FIG. 4  is a perspective view of a plug  40 . 
         FIG. 5  illustrates a process of fitting a plug  40  to a plug receiving hole  30 . 
         FIG. 6  is a process of fitting a plug  40  to a plug receiving hole  30 . 
         FIG. 7  is a process of fitting a plug  40  to a plug receiving hole  30 . 
         FIG. 8  is an enlarged view of part of a member for semiconductor manufacturing apparatus  110  in a cross section taken vertically. 
         FIG. 9  is an enlarged view of part of a member for semiconductor manufacturing apparatus  210  in a cross section taken vertically. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferable embodiments of the present invention will be described with reference to the drawings.  FIG. 1  is a cross-sectional view taken vertically through a member for semiconductor manufacturing apparatus  10 ,  FIG. 2  is a plan view of a ceramic plate  20 ,  FIG. 3  is an enlarged view of part of the member for semiconductor manufacturing apparatus  10  illustrated in  FIG. 1 , and  FIG. 4  is a perspective view of a plug  40 . 
     The member for semiconductor manufacturing apparatus  10  includes a ceramic plate  20 , plug receiving holes  30 , gas outlet ports  28 , plugs  40 , gas flow paths  46 , and a cooling plate  60 . 
     The ceramic plate  20  is a ceramic disc (for example, with a diameter of 300 mm and a thickness of 5 mm) formed from an alumina sintered body or an aluminum nitride sintered body. The one surface of the ceramic plate  20  serves as a wafer placement surface  20   a . The ceramic plate  20  includes a built-in electrode  22 . As illustrated in  FIG. 2 , a seal band  21   a  is disposed on the wafer placement surface  20   a  of the ceramic plate  20  along the outer edge, and multiple circular protrusions  21   b  are disposed on all over the wafer placement surface  20   a . The seal band  21   a  and the circular protrusions  21   b  have the same height, which is, for example, several micrometers to several tens of micrometers. The electrode  22  is a planar mesh electrode used as an electrostatic electrode, and a DC voltage is applicable to the electrode  22 . When a DC voltage is applied to the electrode  22 , a wafer W is adsorbed and fixed to the wafer placement surface  20   a  with electrostatic adsorption. When the application of a DC voltage is removed, the wafer W adsorbed and fixed to the wafer placement surface  20   a  is released. The electrode  22  is also used as a RF electrode. Specifically, an upper electrode (not illustrated) is disposed above the wafer placement surface  20   a . When high-frequency power is applied across parallel-plate electrodes formed from the plate electrode and the electrode  22  installed in the ceramic plate  20 , plasma occurs. The electrode  22  has a through-hole  22   a  (refer to  FIG. 3 ) to receive each plug  40 . A predetermined insulation distance is secured between each plug  40  and the corresponding through-hole  22   a  in the electrode  22 . 
     The multiple (for example, 12 or 24 equidistantly formed in the circumferential direction) plug receiving holes  30  are closed-end tubular holes formed in a surface  20   b  of the ceramic plate  20  opposite to the wafer placement surface  20   a . Each plug receiving hole  30  has a substantially cylindrical shape (for example, with an opening diameter of 8 mm and a full length of 4 mm). As illustrated in  FIG. 3 , a boundary between a bottom surface  31  and a side surface  32  forms a bevel  33 . 
     The gas outlet ports  28  are holes with a small diameter (for example, a diameter of 0.1 mm) and extending in a thickness direction through the ceramic plate  20  at a portion corresponding to a bottom wall of each plug receiving hole  30 . The multiple gas outlet ports  28  are formed for each plug receiving hole  30 . 
     Each plug  40  is a closely-packed ceramic member (for example, with a maximum outer diameter of 8 mm and a full length of 4 mm), and received in the corresponding plug receiving hole  30 . Preferably, each plug  40  is formed from a ceramic material the same as that of the ceramic plate  20 . A stepped portion  44  is disposed on a side surface of each plug  40  along the circumference of the plug  40 . Each plug receiving hole  30  and the corresponding plug  40  are in contact with each other in an area of the plug receiving hole  30  from a position deeper than the stepped portion  44  of the plug  40  to a position before reaching a circular recess  48  formed to oppose the gas outlet ports  28 . A gap G is formed between each plug receiving hole  30  and the corresponding plug  40  in an area of the plug receiving hole  30  shallower than the stepped portion  44 . This gap G receives a plug support member  50  made of an adhesive material. Examples of the adhesive material includes silicone resin, epoxy resin, and acrylic resin. Here, silicone resin is preferable. Each plug  40  has a first taper portion  41  having a diameter gradually decreasing toward an opening  30   a  of the plug receiving hole  30 . The gap G between the first taper portion  41  and the plug receiving hole  30  is thus gradually widened toward the opening  30   a  of the plug receiving hole  30 . The plug support member  50  receives the first taper portion  41  of the plug  40  from below. Each plug  40  includes a second taper portion  42  having a diameter gradually decreasing toward the bottom surface  31  of the plug receiving hole  30 . The second taper portion  42  is in contact with the bevel  33  of the plug receiving hole  30 . Each plug  40  has a gas flow path  46  inside. 
     The gas flow path  46  is continuous with the gas outlet ports  28  and allows gas flow in a thickness direction of the plug  40 . In the present embodiment, the gas flow path  46  runs helical to pass through the plug  40  in the thickness direction. The surface of the plug  40  opposing the bottom surface  31  of the plug receiving hole  30  has a circular recess  48 . The circular recess  48  connects the gas flow path  46  and the multiple gas outlet ports  28  to each other. 
     For example, the plug  40  may be manufactured by sintering a compact formed a 3D printer or by mold casting. The details of mold casting are disclosed in, for example, Japanese Patent No. 5458050. Mold casting involves injecting, into a forming space of a forming die, a ceramic slurry containing ceramic powder, a solvent, a dispersant, and a gelling agent, and gelatinizing the ceramic slurry by causing the gelling agent to initiate a chemical reaction to form a compact in the forming die. In mold casting, a compact may be manufactured by using, as a forming die, an outer die and a core (a die with the same shape as the gas flow path  46 ) formed from a material with a low melting point such as wax to be formed in the forming die, and by then removing the forming die with melting or eliminating the forming die by heating the forming die to a temperature higher than or equal to the melting point. 
     The cooling plate  60  is a disk made of a metal such as metallic aluminum or an aluminum alloy (a disk with a diameter the same as or larger than the diameter of the ceramic plate  20 ). The cooling plate  60  has a coolant flow path  62  in which a coolant circulates and a gas supply channel  64  to supply backside gas to the plug  40 . The gas supply channel  64  includes annular gas collectors  64   a  concentric with the cooling plate  60  in a plan view, a gas introduction portion  64   b  that introduces gas from the undersurface of the cooling plate  60  to the gas collectors  64   a , and gas distributors  64   c  that distribute gas to the plugs  40  from the gas collectors  64   a . The cooling plate  60  is bonded to the ceramic plate  20  with a resin bonding sheet  70 . The bonding sheet  70  has, at a portion opposing the plug receiving hole  30 , a hole  72  with a diameter the same or slightly larger than the opening diameter of the plug receiving hole  30 . The cooling plate  60  may be joined to the ceramic plate  20  with brazing filler metal instead of the bonding sheet  70 . 
     An example of use of the member for semiconductor manufacturing apparatus  10  with this structure will be described now. First, the member for semiconductor manufacturing apparatus  10  is installed in a chamber not illustrated, and the wafer W is placed on the wafer placement surface. The chamber is decompressed with a vacuum pump and adjusted to have a predetermined degree of vacuum, and a DC voltage is applied to the electrode  22  of the ceramic plate  20  to cause electrostatic adsorption to adsorb and fix the wafer W to the wafer placement surface. Thereafter, the inside of the chamber is changed to a reactant gas atmosphere at a predetermined voltage (for example, several tens to several hundreds of Pa). In this state, a high frequency voltage is applied across an upper electrode, not illustrated, disposed at the ceiling of the chamber and the electrode  22  of the member for semiconductor manufacturing apparatus  10  to cause plasma. Instead of applying a high frequency voltage across the upper electrode and the electrode  22 , a high frequency voltage may be applied across the upper electrode and the cooling plate  60 . The surface of the wafer W is etched with the plasma thus caused. If the plug  40  has a gas flow path that passes straight through in the thickness direction of the inside of the plug  40 , the plasma thus caused may cause an electric discharge between the wafer W and the cooling plate  60  via the gas flow path. In the present embodiment, however, the gas flow path  46  of the plug  40  is helical, and this structure can prevent such an electric discharge. A coolant circulates in the coolant flow path  62  of the cooling plate  60 . Backside gas such as helium is introduced into the gas supply channel  64  from a gas cylinder, not illustrated. The backside gas flows through the gas supply channel  64 , the gas flow paths  46 , and the gas outlet ports  28  to be discharged to and enclosed in a space between the back surface of the wafer W and a portion of the wafer placement surface  20   a  where the seal band  21   a  and the circular protrusions  21   b  are not disposed. The backside gas facilitates thermal conduction between the wafer W and the ceramic plate  20 . 
     A method for manufacturing the member for semiconductor manufacturing apparatus  10  will now be described.  FIGS. 5 to 7  illustrate a process of fitting each plug  40  to the corresponding plug receiving hole  30  of the ceramic plate  20  in the process of manufacturing the s member for semiconductor manufacturing apparatus  10 . 
     First, the ceramic plate  20  and the plug  40  are prepared (step (a)). The ceramic plate  20  and the plug  40  are described above. 
     Subsequently, the plug  40  is inserted into the plug receiving hole  30  of the ceramic plate  20  (step (b), refer to  FIG. 5 ). Specifically, the ceramic plate  20  is placed while having the opening  30   a  of the plug receiving hole  30  facing upward. The plug  40  is picked up while having the circular recess  48  facing downward, and inserted into the plug receiving hole  30 . Thus, as illustrated in  FIG. 6 , the plug receiving hole  30  and the plug  40  come into contact with each other in an area of the plug receiving hole  30  from a position deeper than the stepped portion  44  of the plug  40  to a position in front of the gas outlet ports  28  (in front of the circular recess  48 ). At this time, the surface of the plug  40  having the circular recess  48  is located on the bottom surface  31  of the plug receiving hole  30 , and the second taper portion  42  comes into contact with the bevel  33 . A gap G is formed between the plug receiving hole  30  and the plug  40  in an area of the plug receiving hole  30  shallower than the stepped portion  44  of the plug  40 . 
     Subsequently, an adhesive  80  is filled in the gap G with a dispenser  82 , and then cured (step (c), refer to  FIGS. 6 and 7 ). Examples of the adhesive  80  include silicone-based, epoxy-based, and acryl-based adhesives. Among these, a silicone-based adhesive is preferable. The adhesive  80  is intercepted at the stepped portion  44 . When the adhesive  80  is injected to the opening  30   a  of the plug receiving hole  30 , a fixed amount of the adhesive  80  can be injected. The adhesive  80  is prevented from reaching the gas outlet ports  28  or the circular recess  48  beyond the stepped portion  44 . In addition, the gap G is widened further toward the opening  30   a  of the plug receiving hole  30 , and facilitates injection of the adhesive  80 . When the adhesive  80  is cured, the adhesive  80  is formed into the plug support member  50 . Thereafter, the surface  20   b  of the ceramic plate  20  opposite to the wafer placement surface  20   a  and the surface of the cooling plate  60  in which the gas distributors  64   c  are open are joined with the bonding sheet  70 . Thus, the member for semiconductor manufacturing apparatus  10  is obtained. 
     When the plug  40  has no stepped portion on the side surface, the adhesive  80  may be applied to the side surface of the plug  40 , and then the plug  40  may be inserted into the plug receiving hole  30 . In this case, the adhesive  80  may be removed by the plug  40  coming into contact with the side surface of the plug receiving hole  30  while being inserted. In contrast, with the above-described method of injecting the adhesive  80  into the gap G prevents removal of the adhesive  80 . Thus, this method secures an adhesive layer. Thus, the adhesive layer improves its durability without a gap left around the plug  40 . 
     In the member for semiconductor manufacturing apparatus  10  described above in detail, the plug receiving hole  30  and the plug  40  are in contact with each other in an area deeper than the stepped portion  44  disposed on the side surface of the plug  40 , a gap G is formed between the plug receiving hole  30  and the plug  40  in an area shallower than the stepped portion  44 , and the plug support member  50  made of an adhesive material is formed in the gap G. Thus, regardless of when the adhesive  80  is injected into the gap G between the plug receiving hole  30  and the plug  40  to manufacture the member for semiconductor manufacturing apparatus  10 , the adhesive  80  is prevented from flowing further beyond the stepped portion  44 , and is prevented from flowing into the gas outlet ports  28 . Thus, the gas outlet ports  28  are prevented from being blocked by the adhesive material supporting the plug  40  or the plug support member  50 . 
     The stepped portion  44  thus provided allows the gap G to be discontinuously formed around the plug  40 . Thus, the circumference of the plug  40  can be reliably bonded with the adhesive  80  while preventing leakage of plasma. The stepped portion  44  thus provided can also reduce the effect of plasma on the plug support member  50  serving as an adhesive layer. 
     The plug  40  also includes the first taper portion  41 . Thus, the plug support member  50  receives the first taper portion  41  of the plug  40  from below, and thus prevents the plug  40  from slipping out of the plug receiving hole  30 . 
     The plug  40  also includes the second taper portion  42 . The outer surface of the second taper portion  42  comes into contact with the bevel  33  of the plug receiving hole  30 , and the electrode  22  is disposed in a plane inside the ceramic plate  20  crossing the second taper portion  42 , and has the through-hole  22   a  to allow the plug  40  to pass therethrough. Thus, the plug  40  including the second taper portion  42  enables reduction of the diameter D 1  (refer to  FIG. 3 ) of the through-hole  22   a  unlike in the case of the plug  40  not including the second taper portion  42  (refer to  FIG. 8 , described below). The helical gas flow path  46  formed inside the plug  40  can be elongated further than in the case where the plug  40  is thinned throughout to fit the through-hole  22   a.    
     The plug  40  is made of a closely-packed ceramic material, and the gas flow path  46  is helical. This structure can prevent plasma from discharging via the gas flow path  46 . 
     The present invention is not limited by the embodiments described above, and may naturally be embodied in various forms within the technical scope thereof. 
     For example, instead of the closely-packed ceramic plug  40 , the above embodiment may include a porous plug with the external shape the same as that of the plug  40 . The porous plug has pores inside, and allows backside gas to flow in the thickness direction. The porous plug thus has no need of including the helical gas flow path  46  inside. When such a porous plug is to be included, the outer surface is preferably coated with a closely-packed ceramic material. Thus, the adhesive can be prevented from permeating into the porous plug. 
     In the above embodiment, a resistance heating element may be embedded in the ceramic plate  20 . This structure can more precisely control the temperature of the wafer W. 
     In the above embodiment, the gas flow path  46  inside the plug  40  is helical, but is not particularly limited to this example. For example, the gas flow path may have a shape with multiple bends (such as a zigzag). Such a structure can also effectively prevent an electric discharge from occurring via the gas flow path. 
     In the above embodiment, the plug  40  may omit the first taper portion  41 . In such a case, the gap G and the plug support member  50  have a uniform width (thickness). 
     In the above embodiment, the plug  40  includes the second taper portion  42 , and the bevel  33  is formed at the plug receiving hole  30 . However, as in the member for semiconductor manufacturing apparatus  110  illustrated in  FIG. 8 , the second taper portion  42  or the bevel  33  may be omitted. In  FIG. 8 , components the same as those in the above embodiment are denoted with the same reference signs. In this structure, a diameter D 2  of the through-hole  22   a  of the electrode  22  is larger than the diameter D 1  according to the embodiment, as the plug  40  and the through-hole  22   a  of the electrode  22  need to be spaced apart from each other by a predetermined insulation distance. 
     In the above embodiment, the stepped portion  44  is disposed on the side surface of the plug  40 . However, as in a member for semiconductor manufacturing apparatus  210  illustrated in  FIG. 9 , instead of the stepped portion  44  disposed on the side surface of the plug  40 , a stepped portion  34  may be disposed on the side surface  32  of the plug receiving hole  30 . In  FIG. 9 , components the same as those of the above embodiment are denoted with the same reference signs. In the member for semiconductor manufacturing apparatus  210 , the plug receiving hole  30  and the plug  40  are in contact with each other in an area of the plug receiving hole  30  from a position deeper than the stepped portion  34  to a position in front of the gas outlet ports  28 . A gap G is formed between the plug receiving hole  30  and the plug  40  in an area of the plug receiving hole  30  shallower than the stepped portion  34 . The plug support member  50  is formed in the gap G. Thus, regardless of when an adhesive is injected into the gap G between the plug receiving hole  30  and the plug  40  to manufacture the member for semiconductor manufacturing apparatus  210 , the adhesive is prevented from flowing further beyond the stepped portion  34 , and is prevented from flowing into the gas outlet ports  28 . Thus, the gas outlet ports  28  are prevented from being blocked by the adhesive material supporting the plug  40  or the plug support member  50 . 
     The present application claims priority from Japanese Patent Application No. 2021-001017, filed on Jan. 6, 2021, the entire contents of which are incorporated herein by reference.