Abstract:
A method and an apparatus for performing the method. The method includes: (a) providing an apparatus, wherein the apparatus comprises (i) a chamber, (ii) a plasma device being in and coupled to the chamber, (iii) a shower head being in and coupled to the chamber, and (iv) a chuck being in and coupled to the chamber; (b) placing the substrate on the chuck; (c) using the plasma device to receive a plasma device gas and generate a plasma; (d) directing the plasma at a pre-specified area on the substrate; and (e) using the shower head to receive and distribute a shower head gas in the chamber, wherein the plasma device gas and the shower head gas are selected such that the plasma and the shower head gas when mixed with each other result in a chemical reaction that forms a film at the pre-specified area on the substrate.

Description:
[0001]    This application is a continuation application claiming priority to Ser. No. 10/908,709, filed May 24, 2005. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to plasma processing, and more specifically, to local plasma processing. 
         [0004]    2. Related Art 
         [0005]    In a typical semiconductor structure fabrication process, the deposition of a film on a wafer can frequently result in the film being thinner on the edge of the wafer than on other parts of the wafer (i.e., under-deposition at wafer edge). In addition, a chemical mechanical polishing (CMP) process performed on the wafer usually has a higher CMP rate at the edge of the wafer than at other parts of the wafer (i.e., over-polish at wafer edge). As a result, integrated circuits formed near the edge of the wafer may be damaged by this nonuniformity. 
         [0006]    Therefore, there is a need for a method (and an apparatus for performing the method) to compensate for the problems of under-deposition and over-polish at the edge of a wafer. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a structure processing method, comprising providing an apparatus, wherein the apparatus comprises (i) a chamber, (ii) a plasma device being in and coupled to the chamber, (iii) a shower head being in and coupled to the chamber, and (iv) a chuck being in and coupled to the chamber; placing a substrate on the chuck; using the plasma device to receive a plasma device gas and generate a plasma; directing the plasma at a pre-specified area on the substrate; and using the shower head to receive and distribute a shower head gas in the chamber, wherein the plasma device gas and the shower head gas are selected such that the plasma and the shower head gas when mixed with each other result in a chemical reaction that forms a film at the pre-specified area on the substrate. 
         [0008]    The present invention also provides a structure processing method, comprising providing an apparatus, wherein the apparatus comprises (i) a chamber, (ii) a plasma device being in and coupled to the chamber, and (iii) a chuck being in and coupled to the chamber; placing a substrate on the chuck; using the plasma device to receive a plasma device gas and generate a plasma; and directing the plasma at a pre-specified area on the substrate, wherein the plasma device gas is selected such that particles of the plasma bombard the pre-specified area on the substrate essentially without chemically reacting with materials of the pre-specified area on the substrate. 
         [0009]    The present invention provides a method (and an apparatus for performing the method) to compensate for the problems of under-deposition and over-polish at the edge of a wafer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  illustrates an apparatus, in accordance with embodiments of the present invention. 
           [0011]      FIG. 2  illustrates a plasma device of the apparatus of  FIG. 1 , in accordance with embodiments of the present invention. 
           [0012]      FIGS. 3-8  illustrate different uses of the apparatus of  FIG. 1 , in accordance with embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  illustrates an apparatus  100 , in accordance with embodiments of the present invention. In one embodiment, the apparatus  100  comprises a chamber  110 , a chuck  120 , a plasma device  130 , and a shower head  140 . 
         [0014]    The chuck  120  is adapted for holding a wafer  150  for processing. The plasma device (also called plasma jet)  130  is adapted for receiving a plasma device gas and then generating a plasma at atmospheric pressure (i.e., around 1 atm) for processing a pre-specified area of the wafer  150 . The shower head  140  is adapted for receiving and distributing a shower head gas into the chamber  110 . 
         [0015]      FIG. 2  illustrates one embodiment of the plasma device  130  of  FIG. 1 , in accordance with embodiments of the present invention. Illustratively, the plasma device  130  comprises (i) a container  210  that also serves as a ground electrode of the plasma device  130 , (ii) a radio frequency electrode  220 , (iii) a gas inlet  230 , and (iv) a nozzle  240 . The plasma device  130  is adapted for receiving the plasma device gas via the gas inlet  230 , creating a plasma inside the container  210 , and outputting the plasma via the nozzle  240 . 
         [0016]    With reference to  FIGS. 1 and 2 , in one embodiment, either or both of the plasma device  130  and the chuck  120  are moved with respect to the chamber  110  such that the plasma output by the plasma device  130  via the nozzle  240  is directed at the pre-specified area of the wafer  150 . In addition, the plasma device gas and the shower head gas are selected such that the plasma output by the plasma device  130  and the shower head gas distributed by the shower head  140  when mixed with each other will result in chemical reactions forming a film (not shown) on the pre-specified area of the wafer  150 . After the film is deposited, if another film (not shown) is needed at another pre-specified area of the wafer  150 , the plasma output is re-directed at the another pre-specified area of the wafer  150 . 
         [0017]    In an alternative embodiment, the plasma device gas is selected such that the plasma output by the plasma device  130  contains high ion densities that (i) drive off volatile constituents on the wafer  150  (i.e., drying) or (ii) modify a thin film (not shown) for the purpose of densification, annealing, curing, or cross-linking in the case of polymeric systems on the wafer  150 . For example, in one embodiment, the plasma device gas includes inert gases (e.g., Ar, etc.) or N 2  so that the resultant plasma contains radicals that drive off rinsing species from the pre-specified area of the wafer  150 . After the pre-specified area of the wafer  150  is dried off, if another pre-specified area of the wafer  150  needs drying, either or both of the plasma device  130  and the chuck  120  are moved with respect to the chamber  110  such that the plasma output by the plasma device  130  via the nozzle  240  is directed at the another pre-specified area of the wafer  150 . The same plasma device gas (i.e., Ar or N 2 ) can be used to densify, anneal, cure, or cross-link a film on the wafer  150  by heating the film to a high temperature. It should be noted that the plasma device gas is also selected such that the resultant plasma essentially does not chemically react with any material of the wafer  150 . 
         [0018]    In one embodiment, the shower head  140  is omitted if the apparatus  100  of  FIG. 1  is to be used to (i) drive off volatile constituents on the wafer  150  (i.e., drying) or (ii) densify, anneal, cure, or cross-link a film on the wafer  150  by heating the film to a high temperature. 
         [0019]      FIGS. 3-8  illustrate different uses of the apparatus  100  of  FIG. 1 , in accordance with embodiments of the present invention. More specifically, with reference to  FIG. 3 , the apparatus  100  ( FIG. 1 ) is used for depositing a film  320  at a pre-specified location on the wafer  150 . For simplicity, hereafter, only the plasma device  130  instead of the entire apparatus  100  of  FIG. 1  is shown in the figures. The positions of the plasma device  130  and/or the chuck  120  with respect to the chamber  110  are such that the nozzle  240  is pointed to the pre-specified location on the wafer  150 . In one embodiment, when the plasma generated by the plasma device  130  exits the plasma device  130  at the nozzle  240 , the plasma is mixed with the shower head gas distributed by the shower head  140  resulting in chemical reactions producing a material that deposits on the pre-specified location on the wafer  150  as the film  320 . The material may also deposit at other areas of the wafer  150  but with negligible amounts. 
         [0020]      FIG. 4  is a table listing some illustrative film materials of the film  320  ( FIG. 3 ) and the corresponding plasma device gas and shower head gas that may be used to create the film  320  ( FIG. 3 ). With reference to both  FIGS. 3 and 4 , for instance, assume the film  320  is to comprise silicon dioxide (SiO 2 ). Then, silane (SiH 4 ) may be used as the showerhead gas, and one or more of the group comprising O 2 , N 2 O, NO, CO 2 , and CO may be used as the plasma device gas. For instance, if oxygen (O 2 ) is used as the plasma device gas, then the following chemical reaction occurs outside the nozzle  240  where the oxygen plasma exits the plasma device  130  and is mixed with the showerhead gas: SiH 4 +O 2 →SiO 2 +2H 2 . As a result, the resultant SiO 2  deposits on the pre-specified location on the wafer  150 . In one embodiment, the pressure of the ambient inside the chamber  110  ( FIG. 1 ) is atmospheric (i.e., 1 atm) during the deposition. The flow rate for oxygen (plasma device gas) in the plasma device  130  is in a range of 10-1,000 sccm (Standard Cubic Centimeters per Minute). The flow rate of silane (showerhead gas) is in a range of 10-1,000 sccm. To maintain the chamber  110  ( FIG. 1 ) at atmospheric pressure, a dilutant gas (e.g., oxygen in this example) may be added in the showerhead gas (in addition to silane) at a flow rate in a range of 100-10,000 sccm. 
         [0021]    As another example, assume the film  320  is to comprise tungsten (W). Then, inert gas (e.g., argon) and hydrogen (H 2 ) may be used as the showerhead gas, and WF 6  may be used as the plasma device gas. Then, the following chemical reaction occurs outside the nozzle  240  where the plasma exits the plasma device  130  and is mixed with the showerhead gas: WF 6 +3H 2 →W+6HF. As a result, the resultant tungsten (W) deposits on the pre-specified location on the wafer  150 . 
         [0022]    With reference to  FIG. 3 , in one embodiment, the film  320  is formed at the edge of the wafer  150  so as to compensate for under-deposition and/or over-polish (i.e., over-planarization) at the edge of the wafer  150 . In general, films (not shown) similar to the film  320  may be formed at locations (not necessarily at the wafer edge) of the wafer  150  that are thinner than average so as to compensate for an earlier over-etching and/or a subsequent under-deposition at these locations (over-etching and under-deposition may occur due to pattern/topology nonuniformity). For example, assume a tungsten layer (not shown) deposited on the wafer  150  using a traditional deposition method is thinner at first areas of high device density than at second areas of low device density. Then, the apparatus  100  of  FIG. 1  may be used to deposit more tungsten (W) at the first areas where the W layer is thinner so as to compensate for the earlier under-deposition of tungsten there. 
         [0023]    In one embodiment, the plasma device  130  can be stationary (i.e., fixed) with respect to the chamber  110  ( FIG. 1 ) while the wafer  150  is rotated around an axis perpendicular to the wafer  150 . Deposition time is such that the resultant film  320  has a thickness  322  not less than the required minimum thickness. For example, assume that a typical SiO 2  film (not shown) deposited on top of the wafer  150  must have a thickness of at least 20 nm, and that the apparatus  100  ( FIG. 1 ) deposits SiO 2  at 2 nm/wafer rotation. As a result, the deposition time (in terms of rotations) must be at least: 20 nm/(2 nm/rotation)=10 rotations in this example. Assume further that it takes 1 sec for the wafer  150  to make one rotation. Then, the deposition time must be at least: 10 rotations×1 sec/rotation=10 sec. 
         [0024]      FIG. 5  illustrates another use of the apparatus  100  ( FIG. 1 ), in accordance with embodiments of the present invention. More specifically, a chip  505  including a copper wire bond landing pad  510  and a gold wire bond  520  is placed on the chuck  120  of the apparatus  100  ( FIG. 1 ). Then, a SiO 2  film  530  is deposited so as to seal off the connection between the copper pad  510  and the gold wire bond  520 . As a result, the connection between the copper pad  510  and the gold wire bond  520  is protected from corrosion. In an alternative embodiment, the film  530  comprises SiN (silicon nitride) instead of SiO 2 . In yet another alternative embodiment, the film  530  comprises first and second layers (not shown) of SiN and SiO 2 , respectively, with the first layer of SiN being sandwiched between and in direct physical contact with the copper wire bond landing pad  510  and the second layer of SiO 2 . Illustratively, the apparatus  100  ( FIG. 1 ) can be used to form the first layer of SiN on the copper wire bond landing pad  510  first, and then form the second layer of SiO 2  on the first layer of SiN resulting in the film  530 . 
         [0025]      FIG. 6  illustrates yet another use of the apparatus  100  ( FIG. 1 ), in accordance with embodiments of the present invention. More specifically, the apparatus  100  of  FIG. 1  is used to deposit a SiO 2  film  620  so as to passivate (seal off) a top surface of a crackstop/through via  610  so as to protect the crackstop/through via  610  from corrosion. The crackstop/through via  610  usually comprises an electrically conducting material (e.g., Al, Cu, and W). Therefore, the SiO 2  film  620  helps prevent corrosion of this electrically conducting material. In an alternative embodiment, the film  620  comprises SiN (silicon nitride) instead of SiO 2 . In yet another alternative embodiment, the film  620  comprises third and fourth layers (not shown) of SiN and SiO 2 , respectively, with the third layer of SiN being sandwiched between and in direct physical contact with the crackstop/through via  610  and the fourth layer of SiO 2 . Illustratively, the apparatus  100  ( FIG. 1 ) can be used to form the third layer of SiN on the crackstop/through via  610  first, and then form the fourth layer of SiO 2  on the third layer of SiN resulting in the film  620 . 
         [0026]      FIG. 7  illustrates yet another use of the apparatus  100  ( FIG. 1 ), in accordance with embodiments of the present invention. More specifically, the apparatus  100  of  FIG. 1  is used to precisely deposit a SiO 2  ring  720  on the wafer  150 . Then, a chip  730  is placed on the wafer  150  and inside the ring  730 . In other words, the ring  720  serves as a positioning reference for the placing of the chip  730 . Because the SiO 2  ring  720  can be placed on the wafer  150  at a pre-specified location with high precision, the chip  730  can be placed on the wafer  150  at the specified location also with high precision. 
         [0027]      FIG. 8  illustrates yet another use of the apparatus  100 , in accordance with embodiments of the present invention. More specifically, the apparatus  100  of  FIG. 1  is used to deposit a ring  820  at a pre-specified location on the wafer  150 . Then, a cooling pad  830  is placed on the ring  820  without being in direct physical contact with the wafer  150 . The cooling pad  830  is adapted for absorbing the heat generated by devices (not shown) formed on the wafer  150  directly beneath the cooling pad  830 . In one embodiment, the ring  820  comprises SiO 2 . 
         [0028]    In summary, with reference to  FIG. 1 , the apparatus  100  may be used to deposit films of different materials at pre-specified locations on the wafer  150 . The apparatus  100  may also be used to (i) drive off volatile constituents on the wafer  150  (i.e., drying) or (ii) modify a thin film (e.g., densification, annealing, curing, or cross-linking of the film) on the wafer  150 . 
         [0029]    In one embodiment, the apparatus  100  has multiple plasma devices (not shown) similar to the plasma device  130  so that (a) multiple films (not shown) similar to the film  320  ( FIG. 3 ) can be simultaneously formed on different pre-specified locations of the wafer  150 , and (b) different pre-specified locations of the wafer  150  can be simultaneously dried by directing the plasma outputs of the multiple plasma devices at the different pre-specified locations of the wafer  150 . 
         [0030]    While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.