Abstract:
There is provided a diffuser for implementing a diffusing process in an equipment for manufacturing semiconductor devices to increase or maximize its productivity. The diffuser comprises a reaction pipe; a plate joined to the underside of the reaction pipe for sealing the reaction pipe and defining a work space therewithin. A plurality of wafers are disposed within the work space. A gas injection tube is provided for supplying a reactive gas to the work space. A plurality of plasma electrodes are disposed adjacent to the gas injection tube for applying high frequency power to a reactive gas to induce a plasma reaction. A protection member is adapted to cover a portion of the plasma electrodes inserted into the reaction tube located under the plurality of wafers, for preventing a substantial amount of polymer from being formed under the reactive tube due to a plasma reaction in the reactive gases

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of Korean Patent Application No. 10-2004-0086552, filed Oct. 28, 2004, the disclosure of which is hereby incorporated herein by reference in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to equipment for manufacturing semiconductor devices, and, more particularly, to a diffuser and to a method for using a diffuser in equipment for manufacturing semiconductor devices.  
         [0004]     2. Discussion of Related Art  
         [0005]     In general, semiconductor devices are manufactured by selectively and repeatedly implementing several processes, such as photography, etching, diffusion, chemical vapor phase deposition, ion implantation, metal deposition, or the like, on a wafer.  
         [0006]     Among the above processes, diffusion is implemented to introduce desired conductive impurities into the wafer under a high temperature atmosphere.  
         [0007]     Diffusion is utilized to thermally diffuse the conductive impurities, such as phosphorous, in single crystal silicon or poly silicon, to heat the wafer under an oxygen atmosphere to obtain a thermal oxide film, or to implement annealing or baking.  
         [0008]     Properties of the oxide film (for example, thickness) are sensitive to internal pressure of the diffusing apparatus which is determined by the gas flow of the conductive impurities supplied into the interior of the diffusion apparatus, the sealed condition of the interior, the discharge of remaining gas containing air, or the like.  
         [0009]     However, when reactive gas which is heated by a heater or plasma reaction during the diffusion process flows under a plurality of wafers, the reactive gas is deposited on an inner wall or a plasma electrode under a relatively low temperature atmosphere to generate a polymer in powder form. The polymer is stripped in a mass from the wall or electrode by cleaning gas in an in-situ process, and is dropped onto a flange or plate placed at a lower end of the wafer. This mass of the polymer become particles which are scattered in the dispersion process to pollute the wafer.  
         [0010]     A diffuser for use in the equipment for manufacturing the semiconductor devices will now be described with reference to the accompanying drawings.  
         [0011]      FIG. 1  is a cross-sectional view of a conventional diffuser for use in equipment for manufacturing semiconductor devices, and  FIG. 2  is a perspective view illustrating the interior of a reaction pipe provided with a gas injection pipe  18  and a plasma electrode  22  shown in  FIG. 1 .  
         [0012]     Referring to  FIGS. 1 and 2 , the conventional diffuser for use in the equipment for manufacturing semiconductor devices includes (a) a bell-shaped reaction pipe  10 , (b) a plate  12  placed under the reaction pipe  10  and moved up to seal the reaction pipe  10 , (c) a boat  14  placed in a center of the plate  12  for inserting a plurality of wafers  26  and a plurality of heater blocks  24  into the reaction pipe  10 , (d) a heater  16  arranged around an outer periphery of the reaction pipe  10  corresponding to the plurality of wafers  26  inserted into the boat  14 , for increasing the temperature of the interior of the reaction pipe  10 , (e) a gas injection pipe  18  inserted into the reaction pipe  10  adjacent to the plate  12 , for injecting reactive gas onto the wafer  26  positioned in an upper portion of the reaction pipe  10 , (f) a gas exhaust pipe  20 , placed opposite to the gas injection tube  18  in the reaction tube  10 , for exhausting the reactive gas injected onto the wafer  26  through the gas injection tube  18 , and (g) a plurality of plasma electrodes  22  installed in parallel adjacent to the gas injection tube  18  in a similar manner as the gas injection tube and applying high frequency power to the reactive gas supplied from the gas injection tube  18  to induce a plasma reaction.  
         [0013]     The plate  12  supports the boat  14  provided with the plurality of wafers  26  and the plurality of heater blocks  24 , and is moved up and down by a lifter which is not shown to simplify the drawings. The heater blocks  24  obstruct the heat applied from the heater  14 .  
         [0014]     The gas injection tube  18 , the plasma electrode  22 , and the gas exhaust tube  20  are inserted from the exterior into a side wall of the reaction tube  10  adjacent to an edge of the plate  12 .  
         [0015]     The gas injection tube  18  inserted into the reaction tube  10  is formed with a plurality of holes (not shown) at regular intervals for injecting the reactive gas towards the wafer  26 . The plasma electrode  22  is made of a conductive metal, but is covered by a tube of insulating material to prevent it from being damaged by reactive gas.  
         [0016]     The conventional diffuser induces reaction in the reactive gas injected from the gas injection tube  18  to diffuse it onto the silicon wafer  26  with predetermined ion implanting energy.  
         [0017]     However, the convention diffuser has the following disadvantages. First, in the reaction tube  10 , the pressure and temperature in the position corresponding to the gas exhaust tube  20  under the heater block  24  is lower than the position corresponding to the wafer  26 . The reactive gases are applied onto the tube by the electrostatic force of the plasma electrode  22 , so that a significant amount of polymer, which indicated by reference numeral  30  in  FIG. 3 , is generated on the tube  10  enclosing the plasma electrode  22 . As a result, a cleaning process has to be frequently conducted to eliminate the polymer  30 , thereby decreasing overall productivity.  
         [0018]     Second, in the course of implementing the in-situ cleaning process of supplying the reactive gas into the reaction tube  10  and inducing the plasma reaction to eliminate the polymer, the polymer  30  generated on the plasma electrode  22  is dropped on the plate  12 , as shown in  FIG. 3 . Additional wet cleaning process has to be implemented to eliminate the polymer  30  dropped on the plate  12 , thereby decreasing the overall productivity as well.  
       SUMMARY  
       [0019]     Therefore, the present invention is directed to provide a diffuser for implementing a diffusing process in an equipment for manufacturing semiconductor devices, which can restrain a polymer from being generated on a heater block or a tube enclosing a plasma electrode under the heater block and decrease a frequency of a cleaning process to eliminate the polymer, thereby increasing or maximizing its productivity.  
         [0020]     Another object of the present invention is to provide a diffuser for implementing a diffusing process in an equipment for manufacturing semiconductor devices, which can prevent a polymer, which is generated on a tube enclosing a plasma electrode, from being dropped in an in-situ cleaning process and prevent a further implementation of a wet cleaning process, thereby increasing or maximizing its productivity.  
         [0021]     A diffuser can comprise a reaction pipe. The reaction pipe is preferably bell-shaped. A plate is located under the reaction pipe for sealing the reaction pipe and defining a work space therewithin. The work space is arranged and structured to contain a plurality of wafers therein. A gas injection tube is provided for supplying a reactive gas to the work space. A plurality of plasma electrodes are disposed adjacent to the gas injection tube for applying high frequency power to a reactive gas to induce a plasma reaction. A protection member is adapted to cover a portion of the plasma electrodes inserted into the reaction tube located under the plurality of wafers for preventing a substantial amount of polymer from being formed under the reactive tube due to a plasma reaction in the reactive gas. The diffuser can also include a boat located in work space for inserting a plurality of wafers and a plurality of heater blocks into the reaction pipe, a heater for increasing temperature in the work space, a gas injection pipe located within the reaction for injecting reactive gas onto the wafers, a gas exhaust pipe for exhausting the reactive gas injected onto the wafer;, a plurality of plasma electrodes located adjacent to the gas injection tube for applying high frequency power to the reactive gas supplied from the gas injection tube to induce a plasma reaction, and a protection member for preventing a substantial amount of polymer from being formed on the plate.  
         [0022]     The gas injection tube preferably injects phosphorous. The plasma electrode applies about 50 to 800 W RF power to induce the plasma reaction in the reactive gas. The NF 3  is the preferred cleaning gas which is injected via the gas injection tube.  
         [0023]     The protection member preferably has an area more than an interval between the plurality of plasma electrodes. The protection member also can also enclose the plurality of plasma electrodes. The protection member can preferably be made of quartz. The diffuser according to claim  1 , wherein the protection member is adapted to form a vacuum therein or be filled with inert gas therein. Preferably, the inert gas is nitrogen or argon, and more preferably, the protection member is filled with the inert gas, and/or the protection member is sealed and/or the protection member is filled with the inert gas which is circulated at a predetermined pressure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:  
         [0025]      FIG. 1  is a cross-sectional view of a conventional diffuser for use in equipment for manufacturing semiconductor devices;  
         [0026]      FIG. 2  is a perspective view illustrating an interior of a reaction pipe provided with a gas injection pipe and a plasma electrode shown in  FIG. 1 ;  
         [0027]      FIG. 3  is a view illustrating a polymer generated in an in-situ cleaning process in a conventional diffuser for use in equipment for manufacturing semiconductor devices;  
         [0028]      FIG. 4  is a cross-sectional view illustrating a diffuser furnace for use in equipment for manufacturing semiconductor devices according to an embodiment of the present invention;  
         [0029]      FIG. 5  is a perspective view illustrating an interior of a reaction pipe provided with a gas injection pipe, a plasma electrode, and a protection member, shown in  FIG. 4 ; and  
         [0030]      FIG. 6  is a perspective view schematically illustrating a diffuser furnace for use in equipment for manufacturing semiconductor devices according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0031]     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided as examples of the invention. Like numbers refer to like elements.  
         [0032]      FIG. 4  is a cross-sectional view illustrating a diffuser furnace which can be used in the equipment for manufacturing semiconductor devices according to an embodiment of the present invention, and  FIG. 5  is a perspective view illustrating the interior of a reaction pipe provided with a gas injection pipe  118 , a plasma electrode  122 , and a protection member  128 , shown in  FIG. 4 .  
         [0033]     Referring to  FIGS. 4 and 5 , the diffuser for use in the equipment for manufacturing semiconductor devices according to an embodiment of the present invention includes a bell-shaped reaction pipe  100  for providing a sealed space, a plate  112  placed under the reaction pipe  100  and moved up to seal the reaction pipe  100 , a boat  114  placed on the plate  112  for inserting plurality of wafers  126  and plurality of heater blocks  124  into the reaction pipe  100 , a heater  116 , arranged around an outer periphery of the reaction pipe  100  corresponding to the plurality of wafers  126  inserted into the boat  114 , for increasing temperature of the interior of the reaction pipe  110 , a gas injection pipe  118  inserted into the reaction pipe  110  adjacent to the plate  112  for injecting reactive gases onto the wafer  126  positioned in an upper portion of the reaction pipe  100 , a gas exhaust pipe  120 , placed opposite to the gas injection tube  118  in the reaction tube  110 , for exhausting the reactive gases injected onto the wafer  126  through the gas injection tube  118 , and a plurality of plasma electrodes  122 , installed in parallel adjacent to the gas injection tube  118  in a similar manner as the gas injection tube, for applying high frequency power to the reactive gases supplied from the gas injection tube  118  to induce a plasma reaction. A protection member  128 , formed from a portion of the plasma electrode  122 , is inserted into the reaction tube  100  to a position corresponding to the heater block  124  under the reaction tube  100 , for preventing a polymer from being generated due to temperature difference between the reactive gases.  
         [0034]     The gas injection tube  118  is formed with a plurality of holes at regular intervals for injecting the reactive gases in a direction parallel with the wafer  126  at the position corresponding to the wafer  126  inserted into the boat  114 . The reactive gases injected from the holes of the gas injection tube are uniformly distributed over substantially the entire surface of the wafers  126  inserted into the boat  114 , and flow to a lower portion of the reaction tube  100  to exhaust through the gas exhaust tube  120 . For example, if the reactive gas is phosphorus, the gas is injected in a flow rate of about 2.5 liters/min through the gas injection tube  118 .  
         [0035]     The plasma electrodes  122  induce the plasma reaction in the reactive gas injected from the gas injection tube  118  to diffuse it onto the silicon wafer  126  with predetermined ion implanting energy at the position adjacent to the gas injection tube  118 . Since the plasma electrode  122  is made of a conductive metal, a tube (not shown) for protecting the entire surface of the plasma electrode  122  inserted into the reaction tube  100  is integrally formed from a side wall of the reaction tube  100  to an upper portion of the boat  114  receiving the wafer  126 .  
         [0036]     For example, a plurality of plasma electrodes  122  can be applied from about 50 to 800 W RF power of about 3.56 MHz radio frequency to induce the plasma reaction in the reactive gas injected from the gas injection tube  118 . At this time, when the RF power is applied to the reactive gas flowing to the lower portion of the reaction tube  100 , the plasma state of reactive gas may be applied onto the tube enclosing the plasma electrode  122  due to the electrostatic force. In addition, the wafer  126  is heated on the upper portion of the reaction tube  100  by the heater  116 , but the reactive gas may be cooled by the heater block  124 , which directly blocks the heat generated from the heater  116 , under the reaction tube  100 . Consequently, the condensation of the reactive gas may cause the generation of the polymer to accelerate.  
         [0037]     The protection member  128  is provided from the portion of the plasma electrode  122  inserted into the reaction tube  100  to the heater block  124  under the lowermost portion of the plurality of wafers  126  which is inserted into the boat  114 , so as to prevent the plasma condensation of the reactive gas due to the RF power applied to the plasma electrode  122  and to prevent the polymer from being generated on the tube enclosing the plasma electrode  122  due to the electrostatic force of the reactive gases flowing under the reaction tube  10 . Specifically, the protection member  128  has an area more than an interval between the plurality of plasma electrodes  122  and a height, preferably of from about 13 centimeters to about 20 centimeters, from the portion inserted into the reaction tube  100  to the heat block. Also, the protection tube is made of quartz having a constant thickness, preferably from about 3 centimeters to about 5 centimeters, in correspondence to a diameter of the tube enclosing the plasma electrode  122  inserted into the reaction tube  100 .  
         [0038]     The protection member  128  may be adapted to include a vacuum therein or to be filled with inert gas therein. Specifically, the protection member  128  may cover the space formed along a constant distance in the tube enclosing the plasma electrodes  122  thereunder, thereby forming a vacuum which is not affected by the RF power applied to the plasma electrode  122 .  
         [0039]     If the RF power of above a given level is applied, discharge may occur in the vacuum state since vacuum permeability is lower relative to the permeability of the inert gas such as nitrogen. The protection member  128  may be enclosed so that the space between the tubes enclosing the plasma electrodes  122  may be filled with the inert gas, such as nitrogen or argon.  
         [0040]     Also, the protection member  128  may be supplied with an additional inert gas from the exterior of the reaction tube  100 , so that the inert gas circulates from the interior of the protection member  128  to the reaction tube  100 . At this time, if the RF power is applied to the plasma electrode  122  in the protection member in which the inert gas is filled or circulated, only the plasma reaction occurs in the protection member  128 , and thus, plasma is not generated on the tube enclosing the plasma electrode  122  in the protection member  128  by the plasma reaction. In addition, since the plasma reaction does not occur in the reaction tube  100  outside the protection member  128 , polymer is not generated by the electrostatic force of the reactive gas.  
         [0041]     If the reactive gas charged to form positive ions by the plasma electrode  122  on the upper portion of the reaction tube  100  in which the wafer  126  is inserted flows in the lower portion of the reaction tube  100 , the reactive gas is pushed towards the gas exhaust tube  120  with a force against the inert reactive gas charged to form positive ions in the protection member  128 . Consequently, it is possible to prevent the polymer from being generated on the outer wall of the protection member  128  due to the reactive gas. Also, if the protection member  128  is heated to a desired temperature by the plasma reaction in the protection gas  128 , it is possible to prevent the reactive gas from being cohered or condensed.  
         [0042]     With the diffuser for use in the equipment for manufacturing the semiconductor devices according to an embodiment of the present invention, the protection member  128  is provided from the portion of the plasma electrode  122  inserted into the reaction tube  100  to the heater block  124  under the wafers  126  inserted into the boat  114 , so as to prevent the polymer from being generated on the tube  100  enclosing the plasma electrode  122  due to the electrostatic force of the reactive gas flowing under the reaction tube  10  of the condensation of the reactive force. Hence, since the period of the cleaning process is reduced, the productivity thereof may be increased.  
         [0043]     On the other hand, if the diffusion processes are implemented several times, the polymer is generated in the reaction tube  100  by the condensation of the reactive gas.  
         [0044]     At this time, without inserting the wafer  126  in the boat  114 , a cleaning gas can be introduced into the reaction tube  100  via the gas injection tube  118 . Simultaneously, the in-situ process causing the plasma reaction can be implemented therein, thereby eliminating the polymer formed in the reaction tube  100 . For example, NF 3  is utilized as the cleaning gas, and NF 3  is injected, preferably at a flow rate of about 0.5 liter/min, via the gas injection tube  118 . In the past, the polymer of a desired thickness is formed on the outer periphery of the tube  100  enclosing the plasma electrode  122  by the condensation of the reactive gas and the electrostatic force generated during the plasma reaction under the heater block, i.e., the reaction tube  100 , through the diffusion process. No the polymer is cleaned with the cleaning gas during the in-situ cleaning process, and is exhausted via the gas exhaust tube  120 . The polymer is striped from the tube with the RF power applied to the plasma electrode  122 , and is dropped on the plate  112 . Hence, in addition to the in-situ cleaning process, an additional wet cleaning process for cleaning the plate  112  may be added.  
         [0045]     With the diffuser for use in the equipment for manufacturing the semiconductor devices according to an embodiment of the present invention, however, the protection member  128  is provided from the portion of the plasma electrode  122  inserted into the reaction tube  100  to the heater block  124 , so as to prevent the polymer from being generated on the tube  100  enclosing the plasma electrode  122  due to the electrostatic force of the reactive gas flowing thereunder. Hence, the polymer generated on the outer wall of the protection member is cleaned by the flow of the cleaning gas.  
         [0046]      FIG. 6  is a perspective view schematically illustrating the diffuser for use in the equipment for manufacturing semiconductor devices according to an embodiment of the present invention. During the in-situ process, the cleaning gas takes part in the plasma reaction in an upper section a of the reaction tube  100  by the RF power applied from the plasma electrode  122 . But the reactive gas does not take part in the plasma reaction in a lower section b of the reaction tube  100  by the protection member  128 . Hence, the lower section of the reaction tube  100  may be cleaned by flow of the cleaning gas.  
         [0047]     With the diffuser for use in the equipment for manufacturing semiconductor devices according to an embodiment of the present invention, the protection member  128  is installed on the tube  100  enclosing the plasma electrode  122  thereunder. Hence, during the in-situ cleaning process to eliminate the polymer which is generated in the reaction tube  100  during several diffusion processes, the polymer is not stripped in a mass from the protection member  128  by the RF power applied from the plasma electrode  122 , and an additional wet cleaning process to clean the polymer is not necessarily, thereby increasing productivity.  
         [0048]     In addition, the above embodiment is merely illustrative of the present invention, and is not limited thereto. For example, width, height and thickness of the protection member  128  to protect the tube, which encloses the outer periphery of the plasma electrode  122  under the reactive tube  100  from the reactive gas, may be varied.  
         [0049]     With the diffuser for use in the equipment for manufacturing the semiconductor devices according to an embodiment of the present invention, the protection member is provided from a portion of the plasma electrode  122  inserted into the reaction tube  100  to the heater block under the wafers inserted into the boat. This is to prevent the polymer from being generated on the tube  100  enclosing the plasma electrode  122  due to the electrostatic force of the reactive gas flowing under the reaction tube  100 . Hence, since the period of the cleaning process is reduced, the productivity thereof may be increased.  
         [0050]     With the diffuser for use in the equipment for manufacturing semiconductor devices according to an embodiment of the present invention, the protection member is installed on the tube  100  enclosing the plasma electrode  122  thereunder. Hence, during the in-situ cleaning process to eliminate the polymer which is generated in the reaction tube  100  during several diffusion processes, the polymer is not stripped in a mass from the protection member by the RF power applied from the plasma electrode  122  In addition, a wet cleaning process to clean the polymer is not necessarily performed, thereby increasing productivity.  
         [0051]     The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.