Abstract:
A new sputter source is disclosed that allows for high rates of deposition at pressures one or two orders of magnitude lower than has previously been obtained. This results in denser films with reduced ion and electron damage to the substrate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to a sputter source and more specifically to a magnetron sputter source, the deposition of materials and more specifically to utilizing a sputter source for the deposition of the material. 
       BACKGROUND OF THE INVENTION 
       [0002]    The deposition of materials using a magnetron enhanced sputter source has been used for more than 30 years. The cross section of a typical circular magnetron sputter source is shown in  FIG. 1 . The sputter source  100  is placed in a vacuum chamber  101 . The vacuum chamber  101  is attached to a vacuum pump (not shown) through a port  109 . Magnets  106  are arranged in 2 concentric rings and attached to an iron yoke  107  resulting in a strong magnetic field  104  that penetrates the target  108  and is largely parallel  110  with the target surface  109 . The strong magnetic field  110 , typically &gt;300 gauss, parallel to the target surface  109  traps the gas ions near the target surface  109  resulting in an increase of several orders of magnitude if ions available for sputtering which results in a corresponding increase in the sputtering rate. A power supply (not shown) DC or RF is electrically attached from the chamber  101  to the target  108 . A gas, typically argon, is metered into the vacuum chamber  101  through a MFC  111  to pressure of typically 3×10E−3 to 1×10E− Torr. The power supply is turned on and the voltage is raised to 300-400 volts for a DC power supply and typically 1-10 KW for an RF supply resulting in sputtering of the target surface  109 . The target material  108  is deposited onto the substrate  105  which is held in place by a chuck  03 , which is typically temperature controlled. Such an arrangement results in a 10 to 100 fold increase in the deposition rate of material from the target  108  onto the substrate surface  105  when compared to sputtering without magnets  106 . 
         [0003]    Various other magnetic arrangements have been used for sputtering, all based on a magnetic field penetrating the surface of a target and a magnetic field parallel to the target surface. An example is shown in  FIG. 2  and is known a hollow cathode  200 . The hollow cathode  200  is placed in a vacuum chamber  201  which is attached to a vacuum pump (not shown) and has a gas injection port  110  the same as in  FIG. 1 . The hollow cathode  200  is placed in a vacuum chamber  201  which is attached to a vacuum pump (not shown) and has a gas injection port  110  the same as in  FIG. 1 . The hollow cathode  200  consists of cylindrical housing  202 . Two rings of magnets  206  are attached to an iron yoke  207  resulting in a strong magnetic field  204  that penetrates the target  208 . A DC or RF power supply (not shown)  3  is attached from the vacuum chamber  201  to the target  208  as was done in  FIG. 1 . Argon is introduced into the vacuum chamber  201  through port  101  and typically metered by a MFC  111  to a pressure of 3-10×10E−3 Torr. The power supply is turned on to 300-400 volts for a DC supply and typically 1 -10 KW for an RF supply. Sputtering occurs where the magnetic field  210  is largely parallel to the target surface  209 . The deposition rate onto the substrate surface is many times greater than the deposition rate without magnets. The hollow cathode  200  results in directional sputtering and is used for sputtering onto substrates with features with aspect ratios, i.e. &gt;5:1. 
         [0004]    Accordingly what is needed is a system and method that allows for high rates of deposition at low pressures. The present invention addresses such a need. 
       SUMMARY OF THE INVENTION 
       [0005]    A new sputter source is disclosed that allows for high rates of deposition at pressures one or two orders of magnitude lower than has previously been obtained. This results in denser films with reduced ion and electron damage to the substrate. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]      FIG. 1  shows an example of a cross section of a typical circular magnetron sputter source. 
           [0007]      FIG. 2  shows an example of prior art which is known as a hollow cathode. 
           [0008]      FIG. 3  shows the present invention, a cross section of the sputter source which consists of a circular housing. 
           [0009]      FIG. 4  is a top view of the present invention and shows the inner ring of magnets and outer ring of magnets arranged in a hexagon. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0010]    The present invention relates generally to a sputter source and more specifically to a magnetron sputter source, the deposition of materials and more specifically to utilizing a sputter source for the deposition of the material. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein. 
         [0011]    The present invention is a “Concentric Hollow Cathode Sputter Source” and is shown in  FIG. 3 .  FIG. 3  is a cross section of the sputter source  300  which consists of a circular housing  302 . A outer hexagon ring of two rows of magnets  306 ,  319  are attached to an iron yoke  302  and an inner hexagonal ring of two rows of magnets  306 ,  319  are attached to an iron yoke  302  and an inner hexagonal ring of two rows of magnets  313 ,  318  are also attached to iron yoke  302 . The iron yoke  302  is the return path for the magnetic flux from all the magnets. 
         [0012]      FIG. 4  is a top view of the present invention and shows the inner ring of magnets  313  and outer ring of magnets  306  arranged in a hexagon. Other configurations are possible such as 3 sides, 4 sides, etc., however 6 sides is the preferred configuration. All the magnets are attached to the iron yoke  307 . 
         [0013]    Referring to  FIG. 3 , the magnetic field has three components. The first component is a magnetic field  314  from the upper row of outer magnets  319  to the lower row of outer magnets  306  that penetrates the outer row of targets  312  and is largely parallel to the outer target surface  309  which traps ions near the surface  309  and results in a high rate of sputtering from the outer target surfaces  312 . A second magnetic field  316  is generated from the inner row of upper magnets  318  to the inner row of low magnets  313  which penetrates the inner targets  308  and is largely parallel to the inner target surface  322  and traps ions at the inner target surface  322  and results in a high rate of sputtering from the inner target surfaces  322 . The third magnetic field  304  is generated from the outer ring of upper magnets  319  to the inner ring of magnets  318 . A similar magnetic field  321  is generated at the bottom of the cavity  315  between the outer ring of lower magnets  306  and the inner ring of lower magnets  313 . Magnetic fields  304  and  321  trap ions and electrons within the cavity  315  which results in increasing the ion density within the cavity  315  and allows sputtering at pressures of 2×10E−5 to 1×10E−2 Torr and preferably at 5×10E−5 to 5×E−4 Torr. Other magnetron sputter sources such as the planar source  100  and the hollow cathode  200  require pressures from 3×10E−3 to 1×10E−2 Torr. The low pressure of this concentric hollow source  300  results in denser sputtered films with less argon or any other gases used in the sputtering process trapped in the deposited film. The lower pressure also increases the mean free path in the vacuum reducing the collusions between the gas molecules and the sputtered material resulting in an increase in the average energy of the arriving sputtered material at the substrate surface, which also increases the deposited material density. A second advantage of trapping the ions and electrons within the cavity  315  is that the number of ions and electrons reaching the substrate surface  105  is greatly reduced as compared to the planar source  100  or the hollow cathode  200 . The reduced ions and electrons reaching the substrate surface  105  greatly reduces ion and electron damage to semiconductor devices fabricated on the substrate surface  105 . 
         [0014]    Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. For example, although the splice is preferably made of a conductive material such as aluminum, it could be made utilizing a non-conductive material which has a conductive capability added to its surface and its use would be within the spirit and scope of the present invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.