Abstract:
Techniques of the present invention are directed to distribution of deposition gases onto a substrate. In one embodiment, a gas distributor for use in a processing chamber is provided. The gas distributor includes a body having a gas deflecting surface and a gas distributor face. The gas deflecting surface defines a cleaning gas pathway. The gas distributor face is disposed on an opposite side of the body from the gas deflecting surface and faces toward a substrate support member. The gas distributor face includes a raised step and at least one set of apertures through the raised step. The at least one set of apertures are adapted to distribute a deposition gas over a substrate positioned on the substrate support member.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to semiconductor manufacturing and, more particularly, to top gas baffle and distributor for delivering gases in semiconductor processing chambers.  
         [0002]     Chemical vapor deposition (CVD) is a gas reaction process used in the semiconductor industry to form thin layers or films of desired materials on a substrate. Some high density plasma (HDP) enhanced CVD processes use a reactive chemical gas along with physical ion generation through the use of an RF generated plasma to enhance the film deposition by attraction of the positively charged plasma ions onto a negatively biased substrate surface at angles near the vertical to the surface, or at preferred angles to the surface by directional biasing of the substrate surface. One goal in the fabrication of integrated circuits (ICs) is to form very thin, yet uniform films onto substrates, at a high throughput. Many factors, such as the type and geometry of the power source and geometry, the gas distribution system and related exhaust, substrate heating and cooling, chamber construction, design, and symmetry, composition and temperature control of chamber surfaces, and material build up in the chamber, must be taken into consideration when evaluating a process system as well as a process which is performed by the system.  
         [0003]     Uneven gas distribution is one problem encountered in semiconductor fabrication, which affects deposition uniformity. In one known chamber configuration, a gas plenum is provided around the perimeter of a processing region and a plurality of nozzles extend radially inwardly to provide gases to the substrate surface. A challenge in such a design is to evenly distribute gases across the substrate surface so that more gas is not provided towards the edge of the substrate than towards the center of the substrate. A top gas nozzle, positioned directly above the substrate support member, can be used to improve deposition uniformity.  
         [0004]     Despite the improvements obtainable by using of a top gas nozzle further improvements and/or alternative techniques are desirable for increasing uniformity of gas distribution on the surface of a substrate.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The present invention provides techniques including a method of introducing a gas into a chamber and an apparatus for processing semiconductors. More particularly, embodiments of the present invention are directed to increasing uniformity of a process gas onto a substrate in a semiconductor processing chamber.  
         [0006]     In one embodiment of the present invention, a gas distributor includes a body having an upper surface adapted to outwardly direct gas away from the body and a lower surface opposite the upper surface. The lower surface has central portion and a recessed peripheral portion separated from the central portion by a step surface. The body further including a gas inlet, a plurality of gas outlets disposed in the step surface and a gas passage connecting the inlet to the plurality of gas outlets.  
         [0007]     In yet another embodiment of the present invention, a substrate processing chamber includes an enclosure having a ceiling and a sidewall and a substrate support capable of supporting a substrate. A gas distributor is positioned centrally above the substrate support. The gas distributor comprising a body including a baffle having an upper surface adapted to outwardly direct gas away from the body and towards the enclosure sidewall, and a lower surface opposite the upper surface and spaced apart from the substrate support. The lower surface has a central portion and a recessed peripheral portion separated from the central portion by a step surface. The body further includes a gas inlet, a plurality of gas outlets disposed in the step surface, and a gas passage connecting the inlet to the plurality of gas outlets. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a cross-sectional view of a previously known gas distributor;  
         [0009]      FIG. 2  is a cross-sectional view of a gas distributor according to an embodiment of the present invention;  
         [0010]      FIGS. 3A and 3B  illustrate a gas distributor according to an embodiment of the invention with clean gas passages;  
         [0011]      FIGS. 4A and 4B  are cross-sectional views of a gas distributor according to another embodiment of the invention;  
         [0012]      FIGS. 5A, 5B ,  5 C,  5 D,  5 E,  5 F, and  5 G show various views and cross-sectional views a gas distributor according to yet another embodiment of the invention;  
         [0013]      FIG. 6  illustrates a three step gas distributor according to an embodiment of the invention;  
         [0014]      FIGS. 7A and 7B  are cross-sectional views of a step for a gas distributor according embodiments of the present invention; and  
         [0015]      FIG. 8  illustrates an exemplary processing chamber having a gas distributor according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The present invention provides techniques including a method of introducing a gas into a chamber and an apparatus for processing semiconductors. More particularly, embodiments of the present invention are directed to increasing uniformity of a process gas onto a substrate in a semiconductor processing chamber.  
         [0017]      FIG. 1  is cross-sectional view of previously known gas distributor for semiconductor processing.  FIG. 1  shows a gas distributor  100  having a gas deflecting surface  102  and a gas distributor face  104 . Gas deflecting surface  102  provides a pathway for cleaning gases during a chamber clean process. Cleaning gases are directed by contoured surface  102  to the chamber walls instead of a substrate support member (not shown) located directly below the gas distributor. The gas distributor  100  is connected to a chamber wall at a proximal portion  106 . A deposition gas can be supplied to the gas distributor  100  at the proximal end  108 . A set of apertures  110  are disposed on the gas distributor face  104  to deliver deposition gases during CVD processes.  
         [0018]      FIG. 2  is a cross-sectional view of a gas distributor according to one embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, the present invention provides a gas distributor  200  for introducing a gas into a semiconductor processing chamber. Gas distributor  200  can be made of any suitable material such as aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), silicon carbide (SiC), zirconium, quartz, sapphire or the like. In this example, gas distributor  200  is a single piece.  
         [0019]     Gas distributor  200  has a gas deflecting surface  202  and a gas distributor face  204 . Gas deflecting surface  202  provides a pathway for cleaning gases during a chamber clean process. Cleaning gases are directed to the chamber walls instead of a substrate support member (not shown) located directly below the gas distributor. The gas distributor  200  is connected to a chamber wall at a proximal portion  206 . During a CVD process, a deposition gas is supplied to the gas distributor  200  at the proximal end  208 . This deposition gas flows through gas distributor  200 , exiting at apertures  210 , and onto a substrate position on the substrate support member.  
         [0020]     As illustrated in  FIG. 2 , apertures  210  are disposed on the gas distributor face  204  at a step  212 , a raised surface. Step  212  can form an oval level or, more preferably, a circular level on gas distributor face  204  having a predetermined diameter. The diameter can range from about 0.01 inches to about 3.00 inches. Step  212  can have a vertical height in a range of about 0.60 inches to about 0.75 inches, and have a slope in a range of about 90 deg to about 15 deg. Step  212  improves gas distribution of gas distributor  200 . In particular, the deposition gas can be dispersed further out to the periphery of the substrate support member as a result of step  212 . Decreasing the slope of step  212  further disperse the gas towards the outside.  
         [0021]     In specific embodiments, gas distributor  200  can have  4 ,  6 ,  8 , or more apertures  210 . These apertures  210  are evenly distributed along the circumference of step  212  or, alternatively, weighted to a particular portion thereof. The placement and number of apertures  210  can be tuned for a specific application to achieve uniform distribution of deposition gas unto the substrate. Likewise, the diameter of apertures  210  can also be tuned. The diameter can be in the range of about 0.005 inches to about 0.250 inches. In a specific embodiment, the diameter of apertures  210  are 0.060 inches.  
         [0022]      FIGS. 3A  (side view) and  3 B (top view) illustrate a gas distributor according to an embodiment of the invention with clean gas passages  314 . Clean gas passages  314  permit a portion of the cleaning gas during a chamber clean process to pass through gas distributor  300  to gas distributor face  304 . Thus, gas distributor face  304  can be more readily cleaned. There are eight clean gas passages  314  in this specific embodiment. However, in alternative embodiment, the number of clean gas passages can be up to about 50 passages. The diameter of each clean gas passage  314  is about 0.06 to about 0.25 inches to allow for efficient cleaning of the gas distributor face  204 .  
         [0023]      FIG. 4A  is a cross-sectional view of a gas distributor  400  according to another embodiment of the invention. Single piece gas distributor  400  has a gas deflecting surface  402  and a gas distributor face  404 . Gas distributor  400  is connected to a chamber wall at a proximal portion  406 . During a CVD process, a deposition gas is supplied to the gas distributor  400  at the proximal end  408 . This deposition gas flows through gas distributor  400 , exiting at apertures  410  and feed holes  416 , and onto a substrate position on a substrate support member (not shown). As illustrated in  FIG. 4B , apertures  410  are disposed on the gas distributor face  404  at a step  412 , and feed holes  416  are disposed at the lateral ends of gas distributor  400 . Feed holes  416  provide for increased deposition at the edges of the substrate to compliment apertures  410  for uniform distribution. The number, placement, and circumference of feed holes  416  and apertures  410  can be tuned for a particular application. In one specific embodiment, gas distributor  400  includes eight feed holes  416  and four apertures  410 . In other embodiments, gas distributor  400  can have feed holes  416  without apertures  410 . Alternatively, gas distributor  400  may include apertures  410  without feed holes  416 .  
         [0024]      FIGS. 5A-5G  show various views and cross-sectional views a gas distributor  500  according to yet another embodiment of the invention. Gas distributor  500  includes clean gas passages  514  and two steps, steps  512 ( a ) and  512 ( b ). Steps  512 ( a ) and  512 ( b ) on gas distributor face  504  can each incorporate a set of apertures. The increased number of steps allows further tuning of gas distribution to improve uniformity. The number and position of apertures included in step  512 ( a ) can differ from step  512 ( b ). For example, apertures  510 ( a ) and  510 ( b ) are not aligned in a radial direction from the center point  518 .  
         [0025]      FIG. 6  illustrates a three step gas distributor  600  according to an embodiment of the invention. Gas distributor face  604  includes steps  612 ( a )-( c ), each with a set of apertures  610 ( a )-( c ) respectively. The three steps provide three zone of control for increased refinement of gas distribution. In addition, due to the shorter length of each aperture, the diameter of apertures  612  can be reduced for improved distribution control. In one specific embodiment, gas distributor  600  is a two piece plenum. In should be noted that other embodiments of the present invention can include 4, 5, 6, or more steps.  
         [0026]      FIGS. 7A and 7B  are cross-sectional views of a gas distributor step according embodiments of the present invention. In  FIG. 7A , a gas distributor step includes a tread portion and a riser portion on a gas distributor face. The riser portion may be perpendicular to the tread portion, or preferably at an angle  710 . Angle  710  can be in the range of about 90 degrees to about 180 degrees. In specific embodiment, angle  710  is about 45 degrees. An aperture on the gas distributor face is disposed on the riser portion of the step. The aperture is perpendicular to the riser portion (having the hole perpendicular to the riser makes the machining of the hole more true with less vibration) or, alternatively, as depicted in  FIG. 7B  at an angle  720 . Angle  720  can, for example, range from about 15 degrees to about 120 degrees.  
         [0027]      FIG. 8  illustrates an exemplary processing chamber system having a gas distributor  811  according to an embodiment of the invention.  FIG. 8  schematically illustrates the structure of an exemplary HDP-CVD system  810  in one embodiment. The system  810  includes a chamber  813 , a vacuum system  870 , a source plasma system  880 A, a bias plasma system  880 B, a gas delivery system  833 , and a remote plasma cleaning system  850 .  
         [0028]     The upper portion of chamber  813  includes a dome  814 , which is made of a ceramic dielectric material, such as aluminum oxide or aluminum nitride, sapphire, SiC or quartz. A heater plate  823  and a cold plate  824  surmount, and are thermally coupled to, dome  814 . Heater plate  823  and cold plate  824  allow control of the dome temperature to within about ±10° C. over a range of about 100° C. to 200° C. Dome  814  defines an upper boundary of a plasma processing region  816 . Plasma processing region  816  is bounded on the bottom by the upper surface of a substrate  817  and a substrate support member  818 .  
         [0029]     The lower portion of chamber  813  includes a body member  822 , which joins the chamber to the vacuum system. A base portion  821  of substrate support member  818  is mounted on, and forms a continuous inner surface with, body member  822 . Substrates are transferred into and out of chamber  813  by a robot blade (not shown) through an insertion/removal opening (not shown) in the side of chamber  813 . Lift pins (not shown) are raised and then lowered under the control of a motor (also not shown) to move the substrate from the robot blade at an upper loading position  857  to a lower processing position  856  in which the substrate is placed on a substrate receiving portion  819  of substrate support member  818 . Substrate receiving portion  819  includes an electrostatic chuck  820  that secures the substrate to substrate support member  818  during substrate processing. In a preferred embodiment, substrate support member  818  is made from an aluminum oxide or aluminum ceramic material.  
         [0030]     Vacuum system  870  includes throttle body  825 , which houses twin-blade throttle valve  826  and is attached to gate valve  827  and turbo-molecular pump  828 . It should be noted that throttle body  825  offers minimum obstruction to gas flow, and allows symmetric pumping. Gate valve  827  can isolate pump  828  from throttle body  825 , and can also control chamber pressure by restricting the exhaust flow capacity when throttle valve  826  is fully open. The arrangement-of the throttle valve, gate valve, and turbo-molecular pump allow accurate and stable control of chamber pressures from between about 1 millitorr to about 2 torr.  
         [0031]     A gas delivery system  833  provides gases from several sources,  834 A- 834 E chamber for processing the substrate via gas delivery lines  838  (only some of which are shown). As would be understood by a person of skill in the art, the actual sources used for sources  834 A- 834 E and the actual connection of delivery lines  838  to chamber  813  varies depending on the deposition and cleaning processes executed within chamber  813 . Gases are introduced into chamber  813  through a gas ring  837  and/or a gas distributor  811 .  
         [0032]     In one embodiment, first and second gas sources,  834 A and  834 B, and first and second gas flow controllers,  835 A′ and  835 B′, provide gas to ring plenum in gas ring  837  via gas delivery lines  838  (only some of which are shown). Gas ring  837  has a plurality of source gas nozzles  839  (only one of which is shown for purposes of illustration) that provide a uniform flow of gas over the substrate. Nozzle length and nozzle angle may be changed to allow tailoring of the uniformity profile and gas utilization efficiency for a particular process within an individual chamber. In a preferred embodiment, gas ring  837  has 12 source gas nozzles made from an aluminum oxide ceramic.  
         [0033]     Gas ring  837  also has a plurality of oxidizer gas nozzles  840  (only one of which is shown), which in a preferred embodiment are co-planar with and shorter than source gas nozzles  839 , and in one embodiment receive gas from body plenum. In some embodiments it is desirable not to mix source gases and oxidizer gases before injecting the gases into chamber  813 . In other embodiments, oxidizer gas and source gas may be mixed prior to injecting the gases into chamber  813  by providing apertures (not shown) between body plenum and gas ring plenum. In one embodiment, third, fourth, and fifth gas sources,  834 C,  834 D, and  834 D′, and third and fourth gas flow controllers,  835 C and  835 D′, provide gas to body plenum via gas delivery lines  838 . Additional valves, such as  843 B (other valves not shown), may shut off gas from the flow controllers to the chamber.  
         [0034]     In embodiments where flammable, toxic, or corrosive gases are used, it may be desirable to eliminate gas remaining in the gas delivery lines after a deposition. This may be accomplished using a 3-way valve, such as valve  843 B, to isolate chamber  813  from delivery line  838 A and to vent delivery line  838 A to vacuum foreline  844 , for example. As shown in  FIG. 8 , other similar valves, such as  843 A and  843 C, may be incorporated on other gas delivery lines.  
         [0035]     Referring again to  FIG. 8 , chamber  813  also has gas distributor  811  and top vent  846 . Gas distributor  811  and top vent  846  allow independent control of top and side flows of the gases, which improves film uniformity and allows fine adjustment of the film&#39;s deposition and doping parameters. Top vent  846  is an annular opening around gas distributor  811 . Gas distributor  811  includes a plurality of apertures in a step according to an embodiment of the present invention for improved gas distribution. In one embodiment, first gas source  834 A supplies source gas nozzles  839  and gas distributor  811 . Source nozzle MFC  835 A′ controls the amount of gas delivered to source gas nozzles  839  and top nozzle MFC  835 A controls the amount of gas delivered to gas distributor  811 . Similarly, two MFCs  835 B and  835 B′ may be used to control the flow of oxygen to both top vent  846  and oxidizer gas nozzles  840  from a single source of oxygen, such as source  834 B. The gases supplied to gas distributor  811  and top vent  846  may be kept separate prior to flowing the gases into chamber  813 , or the gases may be mixed in top plenum  848  before they flow into chamber  813 . Separate sources of the same gas may be used to supply various portions of the chamber.  
         [0036]     System controller  860  controls the operation of system  810 . In a preferred embodiment, controller  860  includes a memory  862 , such as a hard disk drive, a floppy disk drive (not shown), and a card rack (not shown) coupled to a processor  861 . The card rack may contain a single-board computer (SBC) (not shown), analog and digital input/output boards (not shown), interface boards (not shown), and stepper motor controller boards (not shown). The system controller conforms to the Versa Modular European (“VME”) standard, which defines board, card cage, and connector dimensions and types. The VME standard also defines the bus structure as having a  16 -bit data bus and 24-bit address bus. System controller  860  operates under the control of a computer program stored on the hard disk drive or through other computer programs, such as programs stored on a removable disk. The computer program dictates, for example, the timing, mixture of gases, RF power levels and other parameters of a particular process. The interface between a user and the system controller is via a monitor, such as a cathode ray tube (“CRT”), and a light pen.  
         [0037]     The above-described arrangements of apparatus and methods are merely illustrative of applications of the principles of this invention and many other embodiments and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.