Abstract:
A coating layer is applied to a semiconductor device fabrication equipment, specifically, to a sidesurface of an inventive target. Characteristics of the coating layer promote adhesion of sputtered particles which may accumulate on the deposition equipment surface. The coating layer therefore reduces the probability that sputtered particles will flake or crumble from the equipment and contaminate a substrate being processed therein.

Description:
FIELD OF THE INVENTION 
     The present invention relates to apparatuses and methods for the fabrication of semiconductor devices. More particularly, the present invention relates to a target that deposits a material layer on a semiconductor device. 
     BACKGROUND OF THE INVENTION 
     Sputtering is a method of depositing a material layer on a semiconductor substrate. A typical sputtering apparatus includes a target and a substrate support pedestal enclosed in a sputtering chamber. The target contains a material that is deposited on a substrate. The target is typically affixed to the top of the sputtering chamber, but is electrically isolated from the sputtering chamber walls. A voltage source maintains the target at a negative voltage with respect to the sputtering chamber walls, creating a voltage differential which excites a gas contained within the sputtering chamber into a plasma. Plasma ions are generated and directed to the target where plasma ion momentum transfers to target atoms, causing the target atoms to be ejected (i.e., to sputter) from the target. The sputtered target atoms deposit on the substrate, thereby forming a thin film. 
     However, a portion of the sputtered target atoms become scattered in the plasma and eventually accumulate on other surfaces within the sputtering chamber, including the sidesurfaces of the target. The sputtered target atoms, which do not directly deposit on the substrate, are referred to as sputtered particles. A portion of the sputtered particles may tend to flake or crumble off the sidesurfaces of the target as the sputtering chamber thermally cycles, particularly when a significant amount of sputtered particles has accumulated thereon. Such flaking or crumbling sputtered particles may settle on, and thereby contaminate the substrate. Accordingly, in order to reduce this type of contamination, a need exists in the semiconductor fabrication field for an apparatus and method that reduces substrate contamination that occurs due to flaking or crumbling of sputtered particles which accumulate on the sidesurfaces of the target. 
     SUMMARY OF THE INVENTION 
     The present invention provides an inventive target having a front surface and one or more sidesurfaces. A coating layer is applied to the inventive sputtering target&#39;s sidesurface. Characteristics of the coating layer promote adhesion between the sputtering target&#39;s sidesurfaces and sputtered particles which may accumulate thereon, thus preventing the accumulated sputtered particles from flaking off or crumbling off the sidesurfaces of the inventive sputtering target and settling onto a substrate positioned therebelow. Accordingly, the present invention may reduce substrate contamination, thereby increasing sputtering chamber yield and reducing substrate costs. In a further aspect, the coating may also be applied to a portion of the target&#39;s backing plate. 
     Other, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic side view of a conventional sputtering chamber; and 
     FIG. 2 is a side view of an inventive target for use in the sputtering chamber of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention provides an inventive target that may reduce substrate contamination that occurs due to flaking or crumbling of substrate particles accumulated thereon. In order to fully understand the inventive target, it is necessary to first describe a conventional sputtering chamber such as that illustrated in FIG.  1 . 
     FIG. 1 is a diagrammatic illustration of a conventional sputtering chamber  11 . The sputtering chamber  11  generally includes a sputtering chamber enclosure wall  13  having at least one gas inlet  15  coupled to a processing gas source  17 , and an exhaust outlet  19  coupled to an exhaust pump  21 . A substrate support pedestal  23  is disposed in the lower portion of the sputtering chamber  11 , and a target  25  is mounted to or forms the upper portion of the sputtering chamber  11  as is conventionally known. The target  25  has a front surface  27  and at least one sidesurface  29 . Typically, targets are disk shaped, and thus have a single, circumferential side surface  29 . An AC power supply  31  is operatively coupled to the substrate support pedestal  23  so that an AC power signal emitted from the AC power supply  31  may couple through the substrate support pedestal  23  to a substrate  35  positioned thereon. 
     The target  25  is electrically isolated from the sputtering chamber enclosure wall  13  by an insulation member  37 . Any sputtered particles, which accumulate on the insulation member  37 , may cause an electrical short circuit between the sputtering chamber enclosure wall  13  and the target  25 . Such an electrical short circuit may cause the sputtering chamber  11  to malfunction. Therefore, a shield  39  is positioned to prevent sputtered particles from accumulating on the insulation member  37  and also to prevent particles from accumulating on the sputtering chamber enclosure surface  13  as particles may crumble therefrom creating a potential source of substrate contamination. 
     The sputtering chamber enclosure wall  13  is preferably grounded so that a negative voltage may be maintained on the target  25  (with respect to grounded sputtering chamber enclosure wall  13 ) via a DC power supply  41 . A controller  43  is operatively coupled to the DC power supply  41 , the gas inlet  15 , the exhaust outlet  19 , and the AC power supply  31 . 
     In operation, during sputtering, a gas (typically argon) is charged into the sputtering chamber  11  through the gas inlet  15  at a selected flow rate regulated by the controller  43 . The controller  43  also regulates the sputtering chamber pressure by throttling the rate at which the gas is pumped through the exhaust outlet  19 . Accordingly, although a constant chamber pressure is maintained during sputtering, a continuous supply of fresh processing gas is supplied to the sputtering chamber  11 . 
     The D.C. power supply  41  applies a negative voltage to the target  25  with respect to the sputtering chamber enclosure wall  13  so as to excite the processing gas into a plasma state. Ions from the plasma bombard the target  25 , causing the target atoms to sputter therefrom. The sputtered target atoms travel along linear trajectories from the target  25  and deposit on the substrate  35 . 
     A portion of the sputtered target atoms become scattered in the plasma and eventually accumulate on other surfaces within the sputtering chamber  11 , including the sidesurface  29  of the target  25 . As stated previously, the sputtered target atoms, which do not deposit on the substrate, are referred to herein as sputtered particles. A portion of sputtered particles, which is not strongly adhered to the sidesurface  29  of the target  25 , may flake or crumble therefrom as the sputtering chamber  11  thermally cycles. Such flaking or crumbling sputtered particles may settle on, and thereby contaminate the substrate  35 . 
     Various approaches have been employed in an effort to reduce the contamination of substrates that occurs due to sputtered particles flaking or crumbling from the sidesurface  29  of the target  25 . For example, one method involves bead-blasting the sidesurface  29  of the target  25  with beads. Bead-blasting increases the roughness of the sidesurface  29 . Typically, bead-blasting creates a surface roughness R A  around 200 micro inch. Roughing the target&#39;s sidesurface  29  increases adhesion between the sidesurface  29  and sputtered particles accumulated thereon. Accordingly, bead-blasting allows the sputtered particles to adhere more strongly to the sidesurface  29  of the target  25 , and the sputtered particles are less likely to flake or crumble therefrom. 
     Beads from the bead blasting process, however, can become embedded in the target&#39;s sidesurface  29  and during subsequent processing may become dislodged therefrom as the sputtering chamber  11  and the target  25  thermally cycle. Such dislodged beads may settle on the substrate  35  and, due to the size of the beads may cause potentially catastrophic substrate contamination. 
     Another method involves periodically etching the sidesurface  29  of the target  25  to increase the roughness thereof. Such periodic etching causes increased chamber downtime, reduced throughput, and increased maintenance costs. Further, etching requires additional auxiliary equipment which increases the overall system cost. 
     Thus, an improved method is needed to reduce substrate contamination that occurs due to flaking or crumbling of sputtered particles which accumulate on the sidesurface  29  of the target  25 , without decreasing productivity or increasing the overall system cost. 
     FIG. 2 is a side view of an inventive target  101 . The inventive target  101  has a front surface  103  and a sidesurface  105 . A coating  107  is applied to the sidesurface  105  of the inventive target  101 . The coating  107  is preferably a metal spray coating (i.e., a metal coating applied via a spray method), as such coatings conventionally have a rough surface finish. The coating  107  preferably has a surface roughness (R A ) greater than 200 micro inches. The coating may also be applied to a portion of the target&#39;s backing plate  108  as shown in FIG.  2 . 
     The coating  107  may be applied via methods such as flame spraying, arc spraying, thermal spraying, and plasma spraying, all of which are conventionally known to those of ordinary skill in the art. To apply the coating, target surfaces which are not to be coated are covered with a mask which is removed after the coating  107  is applied to the target  101 &#39;s sidesurface  105 . The coating  107  is preferably of sufficient thickness so as to prevent crumbling of sputtered particles. Although the thickness will depend on the specific sputtering process being performed, for most processes coating thicknesses greater than 200 nm (e.g., in the range of 200 nm-1100 nm) is sufficient. Further, the coating  107  comprises a material having a thermal coefficient of expansion similar to that of the sputtered particles accumulated on the sidesurface  105  of the inventive target  101 . Most preferably the coating  107  comprises the same material as the target  101 ; for example, if the inventive target material is aluminum, the coating  107  may be flame sprayed aluminum or may be a flame sprayed composite material which contains aluminum. 
     In operation, during sputtering, a gas (typically argon), is charged into the sputtering chamber  11  (FIG. 1) through the gas inlet  15  (FIG. 1) at a selected flow rate regulated by the controller  43  (FIG.  1 ). The D.C. power supply  41  (FIG. 1) applies a negative voltage to the inventive target  101  with respect to the sputtering chamber enclosure wall  13  (FIG. 1) so as to excite the processing gas into a plasma state. Ions from the plasma bombard the inventive target  101  causing the target atoms to sputter therefrom. The sputtered target atoms travel along linear trajectories from the inventive target  101  and deposit on the substrate  35  (FIG.  1 ). A portion of the sputtered target atoms become scattered in the plasma and eventually accumulate on other surfaces within the sputtering chamber  11  (FIG.  1 ), including the coated sidesurface  105  of the inventive target  101 . As stated previously, the sputtered target atoms which do not deposit on the substrate are referred to as sputtered particles. 
     The roughness of the coating  107  may significantly increase adhesion between the sidesurface  105  of the inventive target  101  and the sputtered particles accumulated thereon. Accordingly, the coating  107  may allow the sputtered particles to adhere strongly to the sidesurface  105  of the inventive target  101 , and may prevent the sputtered particles from flaking off or crumbling therefrom as the sputtering chamber  11  and the inventive target  101  (FIG. 1) thermally cycle. 
     With use of the present invention, greater than 600 kWh of sputtering may occur without needing target replacement due to flaking or crumbling of accumulated material from the sidesurface  105  of the inventive target  101 . Thus, an improvement may be realized over prior art targets that may exhibit flaking or crumbling of accumulated material from bead blasted target sidesurfaces at least as early as 250 kWh. The kWh is a measure of target erosion. Accordingly, the present invention may reduce substrate contamination and may eliminate the need for bead-blasting or etching, thereby increasing deposition chamber yield and reducing substrate costs. 
     The foregoing description discloses only the preferred embodiments of the invention, modifications of the above disclosed apparatus and method which fall within the scope of the invention will be readily apparent to those of ordinary skill in the art. For instance, although the present invention has been described primarily as applied to a target, any surface within the sputtering chamber  11  may benefit from use of the present invention. The invention may also be used within a conventional high-density plasma-type sputtering chamber having a coil (not shown). 
     Accordingly, while the present invention has been disclosed in connection with the preferred embodiments thereof, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention, as defined by the following claims.