Abstract:
A vertical single wall reaction tube type batch processing furnace can reduce the generation of particles. A method of removing native oxide film by fluoride gas can enhance the efficiency of utilization of gas. A method of exciting reaction gas by a catalyst at high temperature can be applied to a batch processing. A method of exciting reaction gas by a catalyst utilizes an oxidizing agent and gas other than an oxidizing agent. The flow rate of gas in the gas injection pipe and that of gas in the exhaust pipe are made to be substantially equal to each other. The gap between two adjacent wafers is made greater than the mean free path of gas. The oxidizing agent is dissociated by a catalyst of Ir, V or Kanthal while the gas other than the oxidizing agent is dissociated by a catalyst of W.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a method of and an apparatus for manufacturing a semiconductor device. More particularly, the method of manufacturing a semiconductor device according to the invention is applicable to a low pressure CVD (chemical vapor deposition) for example SiN, SiO 2 , amorphous Si, poly-Si or the like, etching, ashing of resist and cleaning of a reaction tube. In the description the wording “etching” refers to dry cleaning for removing the native oxide film formed on the silicon exposed in a contact hole for burying an electrode material such as poly-Si, doped poly-Si, SiO 2 , SiN, SiON, TiSi 2 , WSi 2  or TiN, or the scum generated by reaction of the resist and silicon. 
         [0003]    2. Related Background Art 
         [0004]    Vertical batch type heating furnaces include the hot wall type and the cold wall type. Hot wall type furnaces are described in Kazuo Maeda: “Beginner&#39;s Book 3: The Semiconductor Manufacturing System for Beginners”, Industrial Research Society, Jul. 5, 1999, 1st ed., 3rd plate, p. 125. Cold wall type furnaces are described in p. 143 of the same book. 
         [0005]    Initially, vertical type heating furnaces were designed to use a single wall reaction tube. However, as elimination of particles was rigorously required, double wall reaction tubes came into the scene so as to draw reaction gas from the annular gap to an exhaust port (“Vertical type CVD System ERECTUS”; ‘Electronic Materials’, March, 1986, SC-6, pp. 98-102). 
         [0006]    The growth conditions in a hot wall double tube type vertical furnace as described for the prior art in U.S. Pat. No. 6,204,194 (Mar. 20, 2001), which was assigned to the applicant of the present patent application, include the number of wafers: 100 to 150, wafer intervals: 5 to 9 mm, flat zone length: 700 to 900 mm, intra-furnace pressure: 0.3 to 1 torr (40 to 133 Pa) and flow rate of introducing reaction gas into furnace: 3 to 7 m/sec (col. 1, 11. 34-43). In such a CVD condition of the prior art, a part of the reaction gas flowing vertically in the reaction tube is engulfed in surfaces from the peripheries of the wafers and hence the growth rate is restricted by the engulfment of the gas, which makes the growth rate slow. Therefore, in the above cited U.S. patent, a high-speed growth CVD is achieved by injecting the reaction gas in parallel with the surfaces of the wafers arranged vertically in the vertical batch processing heating furnace using a single wall reaction tube. In terms of reaction kinetics, under the condition of high temperature as diffusion rate-determining, all the reaction gas is injected at high speed in parallel with the wafer surfaces in order to accelerate a diffusion. 
         [0007]    WO01/173832 Publication, which was applied by the applicant of the present patent application, proposes an improvement to a method of removing the native oxide film in a contact hole by means of etching gas that is excited by a microwave. 
         [0008]    With the method described in the above cited patent document, the native oxide film, which is SiO 2  film, in a contact hole is removed typically by etching to 5 to 20 angstroms. SiO 2  is transformed into complex Si 6 (NH 4 ), which can easily be decomposed and evaporated at low temperature. It is known that the complex producing reaction shows a high reaction rate at temperature between 10 and 25° C. but stops at 60° C. 
         [0009]    U.S. Pat. No. 4,237,150, proposes a method of dissociating silane into atomic hydrogen and carbon and forming hydrogenated amorphous silicon film by heating silane at 1,400˜1,600° C. in vacuum of 10 −6  to 10 −4  torr by means of tungsten or carbon foil. 
         [0010]    A method of utilizing a hot heating medium (to be referred to as “hot gas dissociation method” hereinafter) similar to the one disclosed in the above quoted U.S. Pat. No. 4,237,150 is reported by Nishimura et. al of Japan Advanced Institute of Science and Technology in “The Bulletin of the Japan Society of Applied Physics”, Aut., 2001, 13P-P11. According to the report, the dissociation/utilization efficiency of reaction gas is high because such a heating medium has a catalytic effect. This method is also introduced to the public by Asahi Shinbun (newspaper) evening issue of Jan. 16, 2002, in an article entitled “Light for Reestablishing the Country by Electronics”. The method is referred to as “Catalytic chemical vapor phase growth method” in the article. 
         [0011]    It is said that, with a hot gas dissociation method, gas molecules are dissociated at a certain probability and seeds that are in some form or another are chemically adsorbed to the catalyst surface so that dissociation/adsorption seeds are thermally desorbed by the hot catalyst and emitted into the reaction space (The Achievement Reporting Session Document for Semiconductor Device Manufacturing Processes Using Cat-CVD Methods, Jun. 4, 2001, p. 15). For SiH 4  and W catalysts, for instance, the term “hot” refers to 1,600° C. or above. Generally, the frequency of collision of a gas molecule with a solid surface is a function of the density (ng) of gas molecules. However, since the chemical formulas of dissociation/adsorption seeds are unknown, the frequency of collision of an SiH 4  molecule in the reaction space is calculated by using the molecule density of SiH 4  and the actual result of CVD is observed in the above cited document. 
         [0012]    With the method disclosed in the above cited U.S. Pat. No. 6,204,194, reaction gas is made to flow upward in the injection pipe and subsequently injected at high speed into the gap between the opposite surfaces of wafers by way of a large number of injection holes arranged at the lateral wall of the injection pipe. The flow rate of reaction gas is maximized when it passes through the injection holes.  FIG. 1  of the accompanying drawings schematically illustrates the gas flow rate of this method. More specifically,  FIG. 1  shows the gas flow rate relative to a horizontal position (horizontal axis) in a vertical reaction tube. While reaction gas is injected from the injection holes at high speed (see dotted line in  FIG. 1 ), it is heated by a heater to produce particles, which are then blown into the reaction space to give rise to defects in the wafers, because reaction gas is driven to flow in the injection pipe at a relatively low rate. 
         [0013]    Therefore, the first object of the present invention is to provide a low pressure CVD method using a vertical batch type heating furnace that can reduce the production of particles. 
         [0014]    With the microwave-excited dry etching method, a microwave generator is arranged around a pipe made of Al 2 O 3  and/or SiO 2  and H 2 , N 2 , NF, or NF 3 +NH 3  is forced to flow through the pipe and excited by a microwave to produce etching gas of active seeds, which is then used for reaction. With this method, a microwave is not irradiated to NF 3  from the anti-particle point of view. Therefore, it reacts with microwave-excited H 2  so as to be transformed into active seeds showing a strong etching effect in order to remove native oxide film. However, it secondarily reacts with Al 2 O 3  and SiO 2 . Al and Si are produced to give rise to particles as a result of the secondary reaction. Additionally, a large volume of NF 3  is required with this method because NF 3  that is to be activated is not directly excited by a microwave. 
         [0015]    Therefore, the second object of the present invention is to provide a method of removing native oxide film by producing a complex that can reduce the rate of consumption of gas containing halogen atoms. 
         [0016]    While a hot gas dissociation method is attracting attention because it can be applied to large surface area wafers and involves a cold process, it is basically used with a single wafer system and no batch system has been realized for it to date. Therefore, the third object of the present invention is to provide a batch type hot gas dissociation system. 
         [0017]    Furthermore, when dissociating an oxidizing agent by means of a hot gas dissociation method, a fierce reaction takes place on the catalyst to give rise to a problem of degrading the catalyst. Therefore, the fourth object of the present invention is to provide a batch type hot gas dissociation system that can produce oxide film. 
       SUMMARY OF THE INVENTION 
       [0018]    According to the invention, the first object is achieved by providing a semiconductor device manufacturing method using a low pressure CVD to dissolve the particle problem, the method comprising: flatly laying two or more than two semiconductor substrates one above another substantially at regular intervals in a single wall reaction tube surrounding the lateral sides of a substrate holding jig and closed at the top so as to be able to remove substrates from the jig, the substrates including or not including dummy wafers; arranging the semiconductor substrates in a vertical type heating furnace provided with a heating means; and bringing the semiconductor substrates into contact with processing gas; the flow rate of gas flowing through a gas injection pipe extending vertically between the single wall reaction tube and the substrate holding jig and the flow rate of gas flowing through a gas exhaust pipe extending vertically between the single wall reaction tube and the substrate holding jig being made substantially equal to each other. 
         [0019]    Referring to  FIG. 1 , the gas flow rates of gases flowing through the respective tubes are made to show a relationship of V 2 ′&gt;&gt;V 1 ′ with conventional methods but V 2 ≈V 1  according to the present invention. Although the relationship tends to be V 2 &gt;V 1  under the influence of the exhaust pump, the difference is preferably not greater than five times. The gas flow rates increase as the gap separating wafers is reduced (see dotted lines (1) and (2)). 
         [0020]    Particles can be reduced by raising the gas flow rates of gases flowing through wafers when the relationship of V 2 ≈V 1  is established because the reaction rate is raised for the reason of the principle described in the above cited U.S. Pat. No. 6,204,194. 
         [0021]    The second and third objects of the invention are achieved by providing a hot gas dissociation system comprising: a substrate holding jig adapted to removably arranging two or more than two semiconductor substrates substantially at regular intervals greater than the mean free path of gas in a reaction tube, the substrates including or not including dummy wafers; a heating means attached, if necessary, to the reaction tube in order to heat the semiconductor substrates; a gas injection means for injecting gas into the reaction tube; an exhaust means for exhausting gas to the outside of the reaction tube; and a heating/catalyzing means for dissociating gas before or after injecting gas from the injection means. 
         [0022]    Note that gas to be used in a hot gas dissociation system in order to achieve the second object includes halogen-containing gas for removing native oxide film. 
         [0023]    The fourth object of the invention is achieved by providing a hot gas dissociation system comprising: a substrate holding jig adapted to removably arranging one or more than one semiconductor substrates in a reaction tube, the substrates including or not including dummy wafers; a heating means attached, if necessary, to the reaction tube in order to heat the semiconductor substrate; a first gas injection means for injecting a first gas other than an oxidizing agent into the reaction tube; a first heating/catalyzing means for dissociating the first gas before or after injecting gas from the gas injection means; a second gas injection means for injecting a second gas of an oxidizing agent into the reaction tube; a second heating/catalyzing means of iridium, vanadium or an Fe—Cr—Al type electric resistor alloy for dissociating the second gas before or after injecting gas from the first gas injecting means; and an exhaust means for exhausting the first and second gases to the outside of the reaction tube; the first gas injection means and the second gas injection means being oriented so as to cause the first and second gases to be mixed with each other after dissociation by the respective catalysts. 
         [0024]    There are various different modes of realization for the gas injection means and the exhaust means to be used for a low pressure CVD method according to the invention. 
         [0025]    For instance, the gas injection means may be a pipe extending vertically in the reaction tube and provided at the lateral wall thereof with injection holes and the exhaust means may be a pipe extending vertically in the reaction tube and provided at the lateral wall thereof with suction holes. In this case, the substrate holding jig holds semiconductor substrates that are flatly stacked in the furnace. 
         [0026]    In another mode of realization, the gas injection means has an opening at a lower part of the reaction tube and the exhaust means is an annular gap formed between the reaction tube and an outer tube coaxially surrounding the reaction tube. In this mode of realization, the exhaust gas flow path formed by utilizing the annular gap can be made to show a large gas conductance. 
         [0027]    In still another mode of realization, the gas injection means is a pipe having an opening at the lateral wall of the reaction tube and the gas exhaust means is an exhaust pipe having an opening at the lateral wall of the reaction tube. In this mode of realization, it is preferable that the vertical position of the gas injection pipe and that of the exhaust pipe substantially agree with each other. 
         [0028]    Additionally, there are various mode of realization for the heating/catalyzing means that is used to achieve any of the second through fourth objects of the invention. For instance, the heating/catalyzing means may be arranged to face the injection holes in the reaction tube. In this mode of realization, a heat shield plate is preferably arranged between the heating/catalyzing means and the semiconductor substrates. In another mode of realization, the heating/catalyzing means may be arranged in the gas injection pipe. 
         [0029]    No heating means such as heater or lamp is required for a hot gas dissociation system according to the invention where the system is applied to an etching or an ashing of resists because dissociated gas heats wafers to 200 to 300° C. However, in the other application a heating means such as heater or lamp may be provided by referring to the heating temperature, which will be described hereinafter. 
         [0030]    The mean free path (λ) of gas that is innegligible to achieve the second and third objects of the present invention is expressed by the formula shown below; 
         [0000]      λ∝ T/d  species 2   ·Pg,  
 
         [0000]    where T represents temperature (K), d species represents the gas diameter (m) and Pg represents the gas pressure (Pa). 
         [0031]    The mean free path (cm) of hydrogen (d species=2.75×10 −10 ) and that of silane (d species=m) are shown in the table below. 
         [0000]    
       
         
               
               
               
             
               
               
               
             
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Pg = 0.1 Torr (13.3 Pa) 
                   
               
             
          
           
               
                 Tg 
                 H 2   
                 SiH 4   
               
               
                   
               
             
          
           
               
                   0° C. (cm) 
                 0.084 
                 0.0106 
               
               
                 2000° C. (cm) 
                 0.70 
                 0.0878 
               
               
                   
               
             
          
         
       
     
         [0032]    The hot gas dissociation method shows a high gas utilization efficiency if compared with the plasma CVD method. This means that the collision frequency (ncol) of gas molecules with substrates is high. The collision frequency (ncol) of gas molecules with a plurality of wafers needs to be uniform for uniformly forming film on the wafers. 
         [0033]      FIGS. 2A and 2B  schematically illustrate collisions of gas molecules with a pair of substrates.  FIG. 2A  shows an instance where the gap (d 1 ) separating the wafers&lt;the mean free path (λ), whereas  FIG. 2B  shows an instance where the gap (d 2 ) separating the wafers&gt;the mean free path (λ). The probability that gas molecules collide with each other before they collide with either of the substrates is higher in the case of  FIG. 2A  than in the case of  FIG. 2B . The instance of  FIG. 2A  is not desirable because the collision frequency of gas molecules with the substrates is uneven and molecules easily regain a ground state from an active state. Although the phenomenon of  FIGS. 2A and 2B  can take place with plasma CVD, it appears more remarkably with a hot gas dissociation method. For the above described reason, in a hot gas dissociation system according to the invention, the gap separating wafers is made not smaller than the mean free path (λ) of gas (d&gt;λ). However, d&gt;&gt;λ is not senseless because it requires a huge reaction space. Therefore, it is preferable that d=1 to 3λ. 
         [0034]    Gas that is to be dissociated by the heating/catalyzing means is selected from substances other than oxidizing agents. Examples of such substances include SiH 4 , Si 2 H 6 , SiH 2 Cl 2 , TEOS, TMOP, NH 3 , PH 3 , B 2 H 6 , H 2 , N 2 , Cl 2 , F, SiCl 4 , BBr, AsH 3 , PCl 3 , WF 6 , TiCl 3 , SiCl 4 , GeCl 4 , NF 3 , SF 6  and CF 3 . They also include TEOS containing oxygen in the compound. Oxidizing agents such as NO 2 , O 2 , CO 2  and O 3  as well as O 2  and O 3  gases that are excited by a high frequency wave of 2.5 GHz, for instance, (also referred to as remote plasma gas) are not dissociated and the third mode of carrying out the present invention as defined in claim  9  is provided with a separate injection means for injecting such an oxidizing agent. 
         [0035]    Unlike the arrangement of claim  9 , in a semiconductor device manufacturing system for achieving the fourth object of the invention, iridium, vanadium or an Fe—Cr—Al type electric resistor alloy, which is well known as Kanthal, is used as oxidizing agent heating/catalyzing means in order to prevent the heater from degrading. 
         [0036]    Gases that can be used for the purpose of the present invention will be described further. 
         [0037]    Gases that can be used to achieve the first object of the invention include those well known in the field of CVD and diffusion. 
         [0038]    Gases that can be used to achieve the third object of the invention and their reaction temperatures are listed below. 
         [0039]    (a) combination of Si 3 N 4  film: SiH 4  and NH 3  (reaction temperature: 750 to 800° C.), combination of SiH 2 Cl 2  and NH 3  (reaction temperature: 750 to 800° C.) 
         [0040]    (b) poly-Si film: SiH 4  (580 to 625° C.), Si 2 H 6  (500 to 550° C.) 
         [0041]    (c) combination of p-doped poly-Si film: SiH 4  and PH 3  (550 to 600° C.) 
         [0042]    For forming oxide film to achieve the third object of the invention, the oxidizing agent is not dissociated by a W heater and is made to react with dissociation gas such as SiH 4 . However, TEOS that contains oxygen in the compound is dissociated by a W heater. To achieve the fourth object of the invention, the oxidizing agent is dissociated by an iridium heater. The oxidizing agent can be selected from a group including NO 2 , O 2 , CO 2  and O 3 . Particularly preferable combinations are listed below. 
         [0043]    (d) SiO 2  film: SiH 4  and NO 2  (about 800° C.), SiH 4  and O 2  (300 to 400° C.), SiH 4  and CO 2  (900 to 1,000° C.), TEOS and O 2  (650 to 670° C.), TEOS (300 to 400° C.), TEOS and O 3  (350 to 400° C.) 
         [0044]    (e) combination of SiON film: SiH 2 Cl 2 , NH 3  and O 2  (700 to 800° C.) 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0045]      FIG. 1  is a schematic illustration of gas flow rate of a method according to the present invention and a conventional method; 
           [0046]      FIGS. 2A and 2B  are schematic illustrations of gas molecules moving between a pair of substrates; 
           [0047]      FIG. 3  is a schematic cross sectional view of a batch processing vertical furnace of the single wall tube type to be used with the first method according to the present invention; 
           [0048]      FIG. 4  is a schematic cross sectional plan view taken along and viewed in the direction of arrows A-A in  FIG. 3 ; 
           [0049]      FIGS. 5A ,  5 B and  5 C are respectively a longitudinal view and front views of a reaction gas injection pipe that can be used for the purpose of the invention; 
           [0050]      FIG. 6  is a schematic cross sectional view of a heating/catalyzing means that can be used for the second through fourth inventions; 
           [0051]      FIG. 7  is a schematic cross sectional view of another heating/catalyzing means; 
           [0052]      FIG. 8  is a schematic cross sectional view of still another heating/catalyzing means; 
           [0053]      FIG. 9  is a schematic longitudinal cross sectional view of a lamp heater that can be used for the purpose of the invention; 
           [0054]      FIG. 10  is a schematic cross sectional view taken along and viewed in the direction of arrows E-E in  FIG. 9 ; 
           [0055]      FIG. 11  is a schematic view of another embodiment of semiconductor device manufacturing system realized to achieve the second object of the invention; 
           [0056]      FIG. 12  is a schematic view of the hot gas dissociation system of the embodiment of  FIG. 11 ; 
           [0057]      FIG. 13  is a schematic cross sectional view taken along and viewed in the direction of arrows A-A in  FIG. 11 ; 
           [0058]      FIG. 14  is a schematic view of another system realized to achieve the fourth object of the invention; 
           [0059]      FIG. 15  is a schematic cross sectional plan view of a system realized to achieve the third and fourth objects of the invention; and 
           [0060]      FIG. 16  is a schematic longitudinal cross sectional view of the system of  FIG. 15 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0061]    Now, the present invention will be described in greater detail by referring to the accompanying drawings that illustrate preferred embodiments of the present invention. 
         [0062]      FIGS. 3 and 4  schematically illustrate a system for carrying out the first method of the present invention. Referring to  FIGS. 3 and 4 , reference symbol  1  denotes the furnace body of a vertical type heating furnace. It is made of fire-resistant and heat-resistant materials and shows a pot-like profile specific to a hot wall furnace closed at the top and open at the bottom. Reference symbol  2  denotes a heating means, or heater, rigidly secured to the inner wall of the furnace body  1  by means of an appropriate jig. The heater  2  is divided into a number of zones, the electric currents supplied to the respective zones are controlled independently. Although not illustrated in detail, current meters V 20 , V 30  are arranged at lower positions of the furnace body  1  and the heater  2 . 
         [0063]    Reference symbol  5  denotes a tower type substrate holding jig that is entirely supported by a lower center shaft  11  so as to be vertically movable and rotatable in the furnace space. The substrate holding jig  5  needs to be rotated when the processing temperature is not higher than 150° C. When the processing temperature is between 350 and 450° C., it is possible to achieve an intra-planar thickness distribution of 5 to 10% without rotating the jig  5 . Reference symbol  3  denotes wafers. One or more than one top wafers and/or one or more than one bottom wafers may be dummy wafers. The gap separating two adjacently located wafers is preferably 5 to 15 mm, more preferably about 10 mm, for 8-inch wafers. A number of annular sections  6  are stacked at regular intervals and rigidly secured to a support column  7  in order to vertically arrange and support wafers  3 . Each annular section  6  is provided with four claws  8  that are arranged at regular intervals of 90° and projecting horizontally toward the central axis of the furnace to hold the peripheral edge of a wafer  3 . 
         [0064]    Reference symbol  10  denotes a base section for rigidly securing the bottom end of the support column  7 . The base section  10  may be a hollow body containing vacuum in the inside. The lower center shaft  11  rigidly fitted to the bottom of the base section  10  is linked to a lifting/rotating mechanism (not shown) through a removable center hole of a bottom plate  12 . 
         [0065]    Reference symbol  13  denotes a quartz-made single wall type reaction tube (to be referred to simply as “reaction tube” hereinafter). A reaction space is provided in the inside. Reference symbol  20  denotes a reaction gas injection pipe and reference symbol  30  denotes reaction gas exhaust pipe. The reaction gas injection pipe  20  is provided with a pair of pipe bodies and the reaction gas exhaust pipe  30  is also provided with a pair of pipe bodies. 
         [0066]    The reaction gas injection pipe  20  preferably has an inner diameter not less than 10 mm. Each pipe body of the reaction gas injection pipe  20  has an introducing section  20   a , a low pressure section  20   b  and an injecting section  20   c  that are arranged continuously in the mentioned order. The introducing section  20   a  is provided with a valve  21  to block any inflow of reaction gas after the end of reaction. During a CVD growth period, the valves  21  of the reaction gas injection pipe  20  is operated so as to be opened and closed to define the conductance in the furnace corresponding to the capacity of the pumps arranged in the reaction gas exhaust pipe  30 . The next low pressure section  20   b  is located off a red-hot region and adapted to reduce the internal pressure and increase the gas flow rate so as to realize a condition of V 2 ≈V 1  as the inner diameter of the tube is rapidly increased there. 
         [0067]    Finally, the injecting section  20   c  extends vertically in the furnace so as to uniformly deliver reaction gas to the stacked wafers  3  in the furnace through injection holes  23 . Some different modes of realizing injection holes  23  will be discussed below. 
         [0068]    For instance, the front end of the reaction gas injection pipe  20  is closed and reaction gas is injected through the injection holes arranged at the lateral wall of the pipe. In this mode, the total cross sectional area (S 1 ) of the injection holes  23  is made greater than the cross section area (S 2 ) of the reaction gas injection pipe  20 C (S 1 &gt;S 2 ) in order to avoid any increase in the gas flow rate due to compressed gas because the inside of a single wall type reaction tube  13  is located closer to the exhaust pump than to the inside of the reaction gas injection pipe  20  and hence the flow rate of reaction gas tends to increase in the single wall type reaction tube  13 . 
         [0069]    In another mode, the front end of the reaction gas injection pipe  20  is not closed but made to be an open end  32  ( FIG. 3 ). Since the cross sectional area (S 1 ′) of the open end  32  provides an effect same as the cross sectional area (S 1 ) of the injection holes, any increase in the gas flow rate due to compressed gas can be avoided when S 1 +S 1 ′&gt;S 2 . The value of the left side of the formula can be increased when the front end of the reaction gas injection pipe is broadened. 
         [0070]    In still another mode, the front end of the reaction gas injection pipe  20  is made to be an open end  32  and all the injection holes  23  are closed. Thus, in this mode, reaction gas is injected from the open end  32 . 
         [0071]    The reaction gas exhaust pipe  30  is an L-shaped pipe provided at the exit side thereof with a valve  31  and at the front end thereof with a suction hole  32 . It is also provided at the lateral wall thereof with suction holes  33  and is connected to an exhaust pump (not shown). 
         [0072]    Current meters V 20 , V 30  are arranged at corresponding positions of the reaction gas injection pipe  20  and the reaction gas exhaust pipe  30  to gauge the respective gas flow rates. 
         [0073]    As shown in  FIG. 4 , a pair of pipe bodies  20   (1) ,  20   (2)  may be arranged side by side for the reaction gas injection pipe  20 . The pipe bodies  20   (j) ,  20   (2)  may have a same length or different respective lengths. Then, different types of gas may be made to flow through the respective pipe bodies  20   (1) ,  20   (2)  having a same length. Reaction gas can be made to flow only to upper wafer(s) or lower wafer(s) by means of pipe bodies  20   (1) ,  20   (2)  having different respective lengths. 
         [0074]    Similarly, a pair of pipe bodies  30   (1) ,  30   (2)  may be arranged side by side for the reaction gas exhaust pipe  30 . 
         [0075]      FIGS. 5A through 5C  illustrate a reaction gas injection pipe  20  whose front end is closed. 
         [0076]      FIG. 5A  is a cross sectional view and  FIGS. 5B and 5C  are front views of different reaction gas injection pipes  20 . As shown in  FIG. 5B , three injection holes  23  have different cross sectional areas with the (upper) one located close to the front end having a large triangular cross section and the (lower) one located close to the rear end having a small triangular cross section. Each injection hole  23  shows an inverted triangular contour and hence has a larger area in an upper section and smaller area in a lower section. With such differentiated contours of the holes, the reaction gas injection holes can be made to inject reaction gas at a same flow rate regardless of their vertical positions. The same effect is achieved by arranging injection holes  23  having a same contour and a same size in a manner as shown in  FIG. 5C . 
         [0077]      FIG. 6  is a schematic cross sectional view of a vertical batch processing heating furnace similar to the one shown in  FIG. 3  but shows only the reaction gas injection pipe  20  and the reaction gas exhaust pipe  30 . The same components are denoted respectively by the same reference symbols. With the hot gas dissociation method that is used with the arrangement of  FIG. 6 , reaction gas is brought into contact with a heater (heating/catalyzing means)  26  made of a wire of tungsten, molybdenum, tantalum, Kanthal (trade name: available from Gadelius AB) or iridium which may or may not be coated with Al 2 O 3  (to be referred to as “tungsten heater  26 ” hereinafter) to produce a reaction gas dissociation phenomenon as described above in “Related Background Art” and subsequently inject reaction gas through the injection holes  23  for batch processing. The internal pressure of the low pressure section  20   b  is preferably 1 to 20 Pa. 
         [0078]    Thus, a system that can achieve the second through fourth objects of the invention can be realized by using the structure of the system of  FIG. 3  and modifying it in a manner as illustrated in  FIG. 6 . Note, however, the following points have to be taken into consideration. 
         [0079]    (a) When the tungsten heater  26  and the wafers  3  are separated from each other by a short distance and the reaction temperature is low, the heater  2  (heating/catalyzing means) is not necessary because the wafers  3  can be heated to reaction temperature by the tungsten heater  26 . 
         [0080]    (b) The oxidizing agent and the gas other than the oxidizing agent need to be injected separately from the respective pipe bodies  20   (1) ,  20   (2)  in order to achieve the third object of the invention. 
         [0081]    (c) One, two or more than two wafers are processed by thermally dissociating etching gas for removing native oxide film in order to achieve the second object of the invention. 
         [0082]    The reaction conditions that has to be satisfied when a hot heating medium such as W is used include the following. 
         [0083]    (1) etching of Si, SiO 2 , SiN using NF 3 , SF 6 , CHF 3 : 
         [0084]    diluted medium: He, electrically energized heating temperature: 2,400° C., pressure: 67 Pa, NF 3  flow rate: 70 sccm (as reported at the above cited Japan Society of Applied Physics). 
         [0085]    (2) CVD of undoped hydrogenated microcrystalline Si: 
         [0086]    SiH 4  flow rate: 2 to 15, heater area: 3 to 50 cm 2 , gas pressure: 0.1 to 13 Pa, substrate temperature: 200 to 300° C., filament temperature: 1,500° C., W filament surface area: 4 cm 2 , (Extended Abstract of the International Pre-workshop on Cat-CVD (Hot-Wide CVD) Process, 1999, 9, 29, Ishikawa Hitech Center, p. 55). 
         [0087]    (3) amorphous Si: 
         [0088]    heater temperature: 1,500 to 1,900° C., SiH 4  flow rate: 10 to 20 sccm, H 2  flow rate: 10 to 40 sccm, heater power: 100 to 600 W, heater area: 5 to 30 cm 2 , gas pressure: 0.1 to 13 Pa, substrate temperature: 150 to 300° C. (Extended Abstract, 1st International Conference on Cat-CVD (Hot-Wide CVD) Process, 2000, 11, 14-17, Kanazawa City). 
         [0089]    (4) poly-Si: 
         [0090]    heater temperature: 1,500 to 1,900° C., SiH 4  flow rate: 0.5 to 10 sccm, H 2  flow rate: 0 to 200 sccm, heater power: 800 to 1,500 W, heater area: 10 to 60 cm 2 , gas pressure: 0.1 to 40 Pa, substrate temperature: 300 to 450° C. (same as (3)). 
         [0091]    (5) SiN x : 
         [0092]    heater temperature: 1,500 to 1,900° C., SiH 4  flow rate: 0.5 to 5 sccm, NH 3  flow rate: 50 to 200 sccm, heater power: 300 to 800 W, heater area: 5 to 30 cm 2 , gas pressure: 0.1 to 13 Pa, substrate temperature: 200 to 300° C. (same as (3)). 
         [0093]    (6) ashing of resist: 
         [0094]    H 2 O, O 2  gas (as reported at the above cited Japan Society of Applied Physics). 
         [0095]      FIG. 7  is a schematic cross sectional view of a tungsten heater that can be used for the purpose of the invention and whose profile and arrangement are different from those of  FIG. 6 . The tungsten heater  26  is arranged between the reaction gas injection pipe  20  and the wafer holding jig. The tungsten heater  26  is guided in a sleeve  27  such as a quarts tube and then extended to the outside of the sleeve  27  to show a U-shaped profile in a hot section that is necessary for the reaction ( 26   a ). Reaction gas injected from the injection holes  23  is brought to contact with the tungsten heater  26   a  and subsequently forms a film on the wafers. In the sleeve  27 , a gap is formed between the tungsten heater  26  and the sleeve  27 . Gas such as N 2  or NH, may be made to flow through the gap in order to protect the tungsten heater  26 . The tungsten heater  26  may be made to show a larger diameter in the sleeve  27  than at the outside of the sleeve  27 . 
         [0096]      FIG. 8  is a schematic transversal cross sectional view of a vertical type furnace whose profile and arrangement are different from those of  FIG. 6  and those of  FIG. 7 . The substrate holding jig is not shown in  FIG. 8 . The tungsten heater  26  is arranged between a pair of parallel pipe bodies  20   (1) ,  20   (2)  of the reaction gas injection pipe  20  and adapted to heat and dissociate gas  28 , which may typically be silane. Then, it supplies reaction gas that is obtained by dissociation toward the wafers  3 . A block plate  29  is arranged to focus the flow of reaction gas produced by dissociation on the tungsten heater  26  and the wafers  3 . 
         [0097]    Beside the parallel pipe bodies  20   (1) ,  20   (2) , a separate oxidizing agent injection pipe may be arranged at an appropriate position in the furnace in order to grow SiO 2  film. 
         [0098]      FIGS. 9 and 10  schematically illustrate an arrangement of lamp heating suited for a reaction conducted at a temperature range below that of 350 to 450° C., particularly at a temperature range between 150 and 300° C., in order to achieve the first object of the invention. Note that only the positions of current meters V 20 , V 30  are shown. 
         [0099]    In  FIGS. 9 and 10 , the components same as those of  FIGS. 3 and 4  are denoted respectively by the same reference symbols. In  FIGS. 9 and 10 , reference symbol  40   a  denotes rod-shaped heating lamps arranged circularly and reference symbol  41  denotes a reflector panel coated with gold (Au) foil, whereas reference symbol  42  denotes a jacket. Cooling water is made to flow between the reflector panel  41  and the jacket  42 . Reference symbol  40   b  denotes a winding lamp heater on the ceiling. Additionally, a purge gas injection pipe  50  for driving out gas in the furnace after the treatment and a separator  51  for protecting a lower part against heat in the furnace are arranged. 
         [0100]    A reflector panel  52  is arranged in the base section  10  in order to reflect heat in the furnace and improve the uniform temperature distribution in the reaction space. Additionally, a top facet quart plate  53  is arranged above the uppermost wafer  3  to raise the hotness of the reaction space. 
         [0101]      FIGS. 11 through 13  schematically illustrate another embodiment of semiconductor device manufacturing system suited for etching native oxide film and adapted to achieve the second object of the invention. In  FIGS. 11 through 13 , the components same as those of  FIGS. 3 and 4  are denoted respectively by the same reference symbols. Note, however, that the reaction gas injection pipe  20  and the reaction gas exhaust pipe  30  are arranged in parallel with each other in a transversal direction and the reaction tube  13  and the pipes  20 ,  30  are made of aluminum. 
         [0102]    Aluminum reacts with N 2 , H 2  and NF 3  to form a stable and inactive film and hence can minimize the production of particles. Additionally, since NF 3  is dissociated and activated by the tungsten heater  26 , its consumption rate is low. 
         [0103]    The tungsten heater  26  shows a profile of a large number of tightly arranged W-shaped patterns as viewed in the direction of gas flow. The rate of reaction of removing native oxide film by excited NF 3  remarkably falls at 60° C. as pointed out earlier and therefore it is necessary to protect the wafers  3  from being heated to such a temperature level by the tungsten heater  26 . A light shield plate  35  is arranged between the tungsten heater  26  and the substrate holding jig  6  in order to protect the wafers  3  against being heated by radiation of heat. On the other hand, a gap is left between the top section of the light shield plate  35  and the inner wall of the reaction tube  13  so that excited NF 3  may get to the wafers  3  by way of the gap. Preferably, the light shield plate  35  has a water cooling structure in the inside so that it may operates as jacket. All the wafers  3  are driven to rotate as the rotary force of the motor  36  is transmitted to the lower center shaft  11  by way of a gear  37 . 
         [0104]      FIG. 14  is a schematic view of another system designed to achieve the fourth object of the invention. It is a cross sectional view similar to that of  FIG. 8 . 
         [0105]    In  FIG. 14 , reference symbol  20   (1)  denotes an injection pipe for injecting gas other than an oxidizing agent, or SiH 4  gas for instance, reference symbol  20   (2)  denotes an injection pipe for injecting an oxidizing agent, or O 2  gas for instance, and reference symbol  26   (1)  denotes a tungsten heater, while reference symbol  26   (2)  denotes an iridium heater and reference symbol  45  denotes a block plate for preventing SiH 4  and O 2  from being mixed with each before dissociation. 
         [0106]      FIGS. 15 and 16  schematically illustrate still another embodiment designed to achieve the fourth object of the invention. The components same as those of  FIGS. 11 through 14  are denoted respectively by the same reference symbols. This system is characterized in that wafers  3  are held not by a grooved column by respective susceptors  39  that are stacked and rigidly secured to a rotary shaft  38 . A gas injection pipe  41  for injecting gas other than an oxidizing agent and an oxidizing agent injection pipe  42  are branched from the reaction tube  13 . 
         [0107]    The iridium heater  26   (2)  of the second embodiment is replaced by a remote plasma generator using a 2.45 GHz microwave.