Patent Document

BACKGROUND 
       [0001]    A plasma processing apparatus generates a plasma in a process chamber for treating a workpiece supported by a platen in the process chamber. A plasma processing apparatus may include, but not be limited to, doping systems, etching systems, and deposition systems. The plasma is generally a quasi-neutral collection of ions (usually having a positive charge) and electrons (having a negative charge). The plasma has an electric field of about 0 volts per centimeter in the bulk of the plasma. In some plasma processing apparatus, ions from the plasma are attracted towards a workpiece. In a plasma doping apparatus, ions may be attracted with sufficient energy to be implanted into the physical structure of the workpiece, e.g., a semiconductor substrate in one instance. 
         [0002]    Turning to  FIG. 1 , a block diagram of one exemplary plasma doping apparatus  100  is illustrated. The plasma doping apparatus  100  includes a process chamber  102  defining an enclosed volume  103 . A gas source  104  provides a primary dopant gas to the enclosed volume  103  of the process chamber  102  through the mass flow controller  106 . A gas baffle  170  may be positioned in the process chamber  102  to deflect the flow of gas from the gas source  104 . A pressure gauge  108  measures the pressure inside the process chamber  102 . A vacuum pump  112  evacuates exhausts from the process chamber  102  through an exhaust port  110 . An exhaust valve  114  controls the exhaust conductance through the exhaust port  110 . 
         [0003]    The plasma doping apparatus  100  may further includes a gas pressure controller  116  that is electrically connected to the mass flow controller  106 , the pressure gauge  108 , and the exhaust valve  114 . The gas pressure controller  116  may be configured to maintain a desired pressure in the process chamber  102  by controlling either the exhaust conductance with the exhaust valve  114  or a process gas flow rate with the mass flow controller  106  in a feedback loop that is responsive to the pressure gauge  108 . 
         [0004]    The process chamber  102  may have a chamber top  118  that includes a first section  120  formed of a dielectric material that extends in a generally horizontal direction. The chamber top  118  also includes a second section  122  formed of a dielectric material that extends a height from the first section  120  in a generally vertical direction. The chamber top  118  further includes a lid  124  formed of an electrically and thermally conductive material that extends across the second section  122  in a horizontal direction. 
         [0005]    The plasma doping apparatus further includes a source  101  configured to generate a plasma  140  within the process chamber  102 . The source  101  may include a RF source  150  such as a power supply to supply RF power to either one or both of the planar antenna  126  and the helical antenna  146  to generate the plasma  140 . The RF source  150  may be coupled to the antennas  126 ,  146  by an impedance matching network  152  that matches the output impedance of the RF source  150  to the impedance of the RF antennas  126 ,  146  in order to maximize the power transferred from the RF source  350  to the RF antennas  126 ,  146 . 
         [0006]    The plasma doping apparatus may also include a bias power supply  190  electrically coupled to the platen  134 . The plasma doping system may further include a controller  156  and a user interface system  158 . The controller  156  can be or include a general-purpose computer or network of general-purpose computers that may be programmed to perform desired input/output functions. The controller  156  may also include communication devices, data storage devices, and software. The user interface system  158  may include devices such as touch screens, keyboards, user pointing devices, displays, printers, etc. to allow a user to input commands and/or data and/or to monitor the plasma doping apparatus via the controller  156 . A shield ring  194  may be disposed around the platen  134  to improve the uniformity of implanted ion distribution near the edge of the workpiece  138 . One or more Faraday sensors such as Faraday cup  199  may also be positioned in the shield ring  194  to sense ion beam current. 
         [0007]    In operation, the gas source  104  supplies a primary dopant gas containing a desired dopant for implantation into the workpiece  138 . The source  101  is configured to generate the plasma  140  within the process chamber  102 . The source  101  may be controlled by the controller  156 . To generate the plasma  140 , the RF source  150  resonates RF currents in at least one of the RF antennas  126 ,  146  to produce an oscillating magnetic field. The oscillating magnetic field induces RF currents into the process chamber  102 . The RF currents in the process chamber  102  excite and ionize the primary dopant gas to generate the plasma  140 . 
         [0008]    The bias power supply  190  provides a pulsed platen signal having a pulse ON and OFF periods to bias the platen  134  and hence the workpiece  138  to accelerate ions  109  from the plasma  140  towards the workpiece  138 . The ions  109  may be positively charged ions and hence the pulse ON periods of the pulsed platen signal may be negative voltage pulses with respect to the process chamber  102  to attract the positively charged ions. The frequency of the pulsed platen signal and/or the duty cycle of the pulses may be selected to provide a desired dose rate. The amplitude of the pulsed platen signal may be selected to provide a desired energy. 
         [0009]    Particles may be generated on the sidewalls of the process chamber  102  during plasma processing. These particles may be of any composition and may include, but are not limited to, silicon, carbon, silicon oxide and aluminum oxide. These particles also may be caused by sputtering of the workpiece or the tool itself. In some embodiments, a liner  193  may be introduced which protects the sidewalls of the process chamber  102 . This liner  193  typically extends the height of the process chamber  102  sidewalls, reaching first section  120 , and along the floor or the process chamber  102 . However, particles may still accumulate on the side surfaces  197  of the liner  193 . Over time, these particles may be subject to external forces that may be greater than the adhesive strength holding them to the side surface  197  of the liner  193 . These external forces may include, but are not limited to, electrostatic forces, shock waves from sudden changes in pressure, and gravitational forces due to continued deposition on the sidewalls or liner  193 . 
         [0010]    When the adhesive strength of these particles is overcome, they free themselves from the sidewalls (or liner  193 ) and may become suspended in the plasma (if active), or fall due to the gravitational force. In some cases, these particles fall atop the workpiece  138 , thereby affecting the functionality of at least a portion of the workpiece  138  and possibly resulting in lower device yields. In other cases, these particles may fall to the floor of the process chamber  102 . However, even in this case, the electrostatic forces caused by the plasma may attract the particles upward from the floor of the process chamber  102 . This force causes the particles to become suspended again in the volume within the chamber and increases the possibility that the particles will ultimately land atop the workpiece  138 , thereby affecting the processing of the workpiece  138  and the device yield. 
         [0011]    One way to minimize the yield decreases of the workpieces  138  is to clean the sidewalls and floor of the process chamber  102  more regularly. Another method requires regular cleaning or replacement of the liner  193 . However, these steps result in additional downtime for the plasma doping apparatus  100 , which lowers the effective yield of the apparatus. 
         [0012]    Therefore, there exists a need for an apparatus that will reduce the possibility of particles landing atop the workpiece and the possibility of particles lowering the device yield. 
       SUMMARY 
       [0013]    According to a first aspect of the disclosure, an apparatus for use within a process chamber is provided. The apparatus includes a liner adapted to cover the sidewalls of the process chamber, with apertures corresponding to various inlets and outlets in the process chamber. In addition, the liner has one or more apertures on its bottom surface, which allow particles to pass through the liner. The liner is designed to be shorter in height than the sidewalls of the process chamber. This allows the liner to be placed within the chamber such that its bottom surface is above the floor of the process chamber. This minimizes the possibility of particles that have fallen onto the process chamber floor becoming re-suspended at a later time. In some embodiments, the apertures in the bottom surface have a width that is less than the thickness of the bottom surface. 
         [0014]    According to a second aspect of the disclosure, a bottom liner is provided. This liner has one or more apertures and can be used in conjunction with a conventional liner and in a process chamber without a liner. The bottom liner is held above the bottom of the process chamber, such as by one or more spacers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like elements are referenced with like numerals, and in which: 
           [0016]      FIG. 1  is a block diagram of a plasma doping apparatus of the prior art; 
           [0017]      FIG. 2  is a block diagram of a plasma doping apparatus consistent with the disclosure; 
           [0018]      FIG. 3  is a first embodiment of a liner consistent with the disclosure; 
           [0019]      FIG. 4  is a second embodiment of a liner consistent with the disclosure; 
           [0020]      FIG. 5  is a bottom view of the embodiment of  FIG. 3 ; 
           [0021]      FIG. 6  shows a spacer used with an embodiment; and 
           [0022]      FIG. 7  is an embodiment of a bottom liner used in conjunction with a conventional liner. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    As described above, traditional plasma processing apparatus may generate particles that adhere to the sidewalls of the process chamber  102 . As described above, a liner  193  may be used to eliminate adhesion to sidewalls of the process chamber  102 , however adhesion to the liner  193  may still present yield issues due to particle buildup and subsequent separation. 
         [0024]    Currently, as shown in  FIG. 1 , the liner  193  extends the entire height of the chamber sidewall, reaching from the first section  120  to the floor of the chamber, and along the floor of the process chamber  102 . In some embodiments, the chamber is cylindrical in shape, thereby resulting in a liner  193  with a bottom surface  196  that is annular, with side surfaces  197  extending upward from the outer circumference of the annular bottom surface  196 . The side surfaces  197  are preferably orthogonal to the bottom surface  196 . In some embodiments, the process chamber  102  may have one or more inlets and/or outlets along the sidewalls of the chamber. For example, the exhaust port  110  may be located along the sidewall of process chamber  102 . In the case of inlets or outlets located along the sidewalls of the process chamber, the liner  193  contains a corresponding aperture  195  in the side surface  197 , thereby allowing the free flow of gasses into and out of the process chamber  102 . 
         [0025]    According to one embodiment of the present disclosure, a liner is defined as shown in  FIG. 2 . The liner  200  may be constructed of aluminum or another electrically conductive material and may be of unitary construction. In some embodiments, the liner  200  is coated, such as with a thermal sprayed silicon. As described above, the liner  200  includes a bottom surface  201 , which is annular in shape. Extending upward from the outer circumference of the bottom surface  201  is a side surface  202 . The side surface  202  of the liner  200  has a height that is less than that of the sidewalls of the process chamber  102 . To insure that the liner  200  protects the sidewalls of the process chamber  102 , spacers  210  are introduced beneath the liner  200 . These spacers  210  elevate the liner  200  so that the upper edge of the side surface  202  of the liner  200  covers the top portion of the sidewall of the process chamber  102 . In other words, the height of the side surface  202  added to the height of the spacer  210  is preferably about the same as the height of the sidewalls in the process chamber  102 . Thus, the liner  200  extends to first section  120 . This allows the liner  200  to protect the sidewalls of the process chamber  102 . 
         [0026]    The spacers  210  are preferably constructed of an electrically conductive material. The spacers  210  may be aluminum bushings, or another structure, and there may be one or more spacers  210  used to support the liner  200 . The height of the spacer may be between 0.25″ and 1.00″ inches tall. In some embodiments, it is preferable that the bottom surface  201  of the liner  200  is no higher than the platen  134 . 
         [0027]      FIG. 6  shows an expanded view of one embodiment of the liner  200  and the spacer  210 . In this embodiment, the liner  200  is installed so as to be offset from the bottom of the process chamber  102  through the use of spacer  210 . A fastener  207  is used to secure the bottom surface  201  of the liner  200  and the spacer  210  to the process chamber  102 . The fastener  207  is preferably electrically conductive and may be a screw or bolt. The spacer creates a volume  310  between the floor of the process chamber  102  and the bottom surface  201  of the liner. 
         [0028]    Referring to  FIGS. 2-4 , it can be seen that the liner  200  may have one or more apertures  305  along its side surface  202 . As described above, these apertures preferably align with inlet or outlets in the sidewalls of the process chamber  102 . Additional apertures may be needed to allow the workpiece  138  and platen  134  to be moved into and out of the process chamber  102 . The side surface  202  of the liner  200  may be between 0.1 and 0.25 inches in thickness. 
         [0029]    As described above, the bottom surface  201  of the liner  200  is preferably annular in shape, where the inner diameter may be greater than or equal to the diameter of the platen  134 , so that the liner  200  fits around the platen  134  in the process chamber  102 . In some embodiments, the inner diameter is between 15.5″ and 16.0″ inches. The outer diameter of the annular bottom surface  201  may be made to be roughly the same as the diameter of the process chamber  102 , so that the side surfaces  202  of the liner  200  are in close proximity to the sidewalls of the process chamber  102  during normal operation, such as less than 0.125″ away. The outer diameter may be between 21.5″ and 22.0″ inches. 
         [0030]    In addition to being elevated from the floor of the process chamber  102 , the liner  200  also has apertures  309  on its bottom surface  201 . These apertures  309  allow particles to fall through the bottom surface  201  and become trapped in the volume  310  defined between the floor of the process chamber  102  and the bottom surface  202  of the liner  200 . In some embodiments, the spacers  210  are affixed to the bottom surface  201  of the liner  200 , such as by fasteners  207  that pass through one or more fastener holes  307 . In one embodiment, the fasteners  207  are screws. 
         [0031]    The apertures  309  can be configured in a variety of ways. For example,  FIG. 3  shows the apertures as concentric curved, arcuate slots.  FIG. 4  shows the apertures are radial rows of holes. In addition, any other pattern of holes, or any shape of hole may be used to form the apertures  309 . 
         [0032]      FIG. 5  shows a bottom view of one embodiment of the bottom surface  201  of the liner  200 . In this embodiment, six fastener holes  307  are provided to allow attachment to a corresponding number of spacers  210 . In this embodiment, the apertures  309  are concentric curved arcuate slots, having a width of about 0.125 inches. The apertures  309  may be positioned as close to one another as desired, as long as sufficient structural support is maintained. In some embodiments, over 40% of the area between the outer diameter  311  and the inner diameter  312  is open. In other words, at least 40% of the material that would exist between the outer diameter  311  and inner diameter  312  is removed by the presence of the apertures  309 . In other embodiments, the percentage of open area on the bottom surface  201  is higher than 50%. The amount of open space maximizes the possibility that a particle will fall through the bottom surface  201  and get trapped in the volume  310  between the bottom surface  201  of the liner  200  and the floor of the process chamber  102 . Although only two sets of concentric slots are shown, the disclosure is not limited to this embodiment; any suitable number of apertures may be used. 
         [0033]    Once particles falls into the volume  310  between the bottom surface  201  of the liner  200  and the floor of the process chamber  102 , it is beneficial that these particles remain trapped within this volume. The constant changes in pressure in the process chamber  102  may cause the particles to be agitated and float upward from the floor of the process chamber  102 . In some embodiments, the apertures are designed to minimize the possibility of particles floating upward through the apertures. In some embodiments, this is achieved by controlling the ratio of the thickness of the bottom surface  201  of the liner  200  to the width of the aperture  309 , also referred to as the aspect ratio of the aperture. For example, in some embodiments, the width of the apertures  309  is about 0.125 inches, while the thickness of the bottom surface of the liner is 0.25 inches. In this case, the ratio of surface thickness to aperture width is 2. In other embodiments, ratios of greater than 1 are suitable. In a two dimensional aperture  309 , the characteristic dimension is typically the smaller dimension. For example, the characteristic dimension of the aperture  309  may be defined as its diameter (in the case of circular apertures  309 ) or its width (in the case of slotted apertures  309 ). 
         [0034]    By creating an aspect ratio greater than 1, the possibility of a particle floating upward and passing through the aperture is reduced. This reduces the number of particles that fall atop the workpiece  138 , and consequently improve the device yield of the apparatus. 
         [0035]    In another embodiment, the liner comprises only a bottom surface.  FIG. 7  shows an embodiment where a liner  700 , having only a bottom surface, is used in a process chamber  102 . In this embodiment, a convention liner  193  is installed to line the sidewalls of the process chamber  102  to facilitate cleaning. Liner  700  is installed on top of liner  193 , and may be secured to liner  193 , or process chamber  102  using fasteners. The liner  700  is offset from the bottom surface  196  of liner  193 , such as by spacers  210 . As described above, the spacers may be electrically conductive and may be aluminum bushings or any other suitable means. In some embodiments, the spacers are between 0.25″ and 1.0″ in height. In some embodiments, the fasteners secure the liner  700  to the pre-existing liner  193 . In other embodiments, the fasteners secure the liner  700  directly to the process chamber  102 , such as by passing through a hole in the pre-existing liner  193 . 
         [0036]    In other embodiments, liner  700  can be used without a pre-existing liner  193 . In this embodiment, the liner  700  is fastened to the floor of the process chamber  102  using fasteners through spacers  210 . 
         [0037]    In the embodiments employing liner  700 , a volume  310  is still created between the floor of the process chamber  102  and the bottom surface of the liner  700 . In addition, the bottom surface of liner  700  comprises a plurality of apertures, as described above with respect to liner  200 . Thus, particles pass through the apertures in liner  700  and become trapped in the volume  310 . In some embodiments, the apertures comprise over 40% of the area of the liner  700 . In some embodiments, the aspect ratio of the apertures is greater than 1. 
         [0038]    Furthermore, the liner  700  has dimensions similar to the bottom surface of liner  200 . In other words, it is annular in shape with an inner diameter of between about 15.5″ and 16.0″ and an outer diameter of between about 21.5″ and 22.0″. The apertures of liner  700  may be of any pattern, such as those shown in  FIGS. 3-5 . 
         [0039]    The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.

Technology Category: 5