Abstract:
A surface is processed by a method comprising: supplying a first gas, e.g. TEOS, through a passage disposed near a surface of a wafer, the first gas being insusceptible to heating by microwave; and supplying a second gas, susceptible to heating be microwave, e.g., H 2 O, through a passage disposed near the wafer surface. A microwave generating unit disposed near the wafer surface irradiates TEOS supplied from the first supplying passage and H 2 O gas supplied from the second gas supplying passage with microwave, selectively heating only H 2 O so that TEOS reacts with H 2 O to form an SiO 2  film on the wafer surface. The inventive method enables precise control of the CVD reaction to form a thin film having good step coverage.

Description:
This application is a divisional of application Ser. No. 08/711,330 filed Sep. 6, 1996 now U.S. Pat. No. 5,868,849. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a surface processing device and a method of processing a surface. It particularly relates to a surface processing device and a method of processing a surface which contemplate improvement in processing a surface of an object to be processed. 
     2. Description of the Background Art 
     Conventionally in the process for manufacturing semiconductor devices, various types of surface processing are performed, typically including film forming and etching. The film forming process includes the CVD method and sputtering. 
     An example of a conventional plasma CVD system will now be described with reference to FIG.  5 . 
     A conventional plasma CVD system  300  has an electrode  306  and a holder electrode  308  contained opposite to each other within an evacuated container  304  which is evacuated by an evacuating device  312 . Holder electrode  308  is grounded. Mounted on holder electrode  308  is a substrate  302  to the surface of which film forming process is applied. Substrate  302  is heated, for example, by a heater  310  within holder electrode  308 . 
     A raw material gas  320  is introduced into evacuated container  304  via gas introducing portion  314  communicating with electrode  306 . As raw material gas  320 , SiH 4  (silane) +H 2 O is used, and recently, TEOS (tetraethoxysilane) +H 2 O or the like has come to be used in view of processing at lower temperature and for planarization of silicon oxide films. 
     In plasma CVD system  300 , gas introducing portion  314  is supplied with TEOS from a gas source  322  and H 2 O from a gas source  324 . Furthermore, mass flow controllers  326  and  328  are provided at supplying passages of TEOS and H 2 O, respectively, and a heater  330  for vaporizing TEOS is also provided at the TEOS supplying passage. 
     Radio frequency (RF) power is supplied to the space between electrode  306  and holder electrode  308  from an RF generator  318  via a matching box  316 . A continuous sign wave is used for the RF power and its frequency is generally 13.56 MHz. 
     In such a plasma CVD system, when raw material gas  320  as described above is introduced into evacuated container  304  to obtain a degree of vacuum, for example, of several hundred mTorr within evacuated container  304  while RF power is supplied to electrode  306  from RF generator  318 , RF electric discharge is generated between electrodes  306  and  308 , causing plasma  332  therebetween. 
     At that time, electrons are trapped in a blocking capacitor, which is generally contained in matching box  316 , so that electrode  306  is negatively charged. This causes positive ions in plasma  332  to accelerate toward and collide against electrode  306  and electrons are thereby generated to maintain plasma  332 . 
     Thus, due to plasma  332 , raw material gas  320  is activated and chemical reactions proceed whereby a silicon oxide (SiO 2 ) film is formed on a surface of substrate  302 . 
     The reaction between the TEOS and H 2 O described above can be expressed by the following chemical formulas: 
     
       
         i) Si(OC 2 H 5 ) 4 +H 2 O→Si(OC 2 H 5 ) 4-n (OH) n +C 2 H 5 OH  (hydrolysis reaction) 
       
     
     
       
         ii) Si(OC 2 H 5 ) 4-n (OH) n →SiO m (OH) j (OC 2 H 5 ) k +H 2 O  (dehydrating condensation reaction) 
       
     
     
       
         iii) SiO 2 +H 2 O+C 2 H 5 OH 
       
     
     TEOS=Si(OC 2 H 5 ) 4    
     silanol=Si(OC 2 H 5 ) 4-n (OH) n    
     silicon polymer=SiO m (OH) j (OC 2 H 5 ) k    
     In the system of reaction between TEOS and H 2 O, silanol is first produced by the hydrolysis reaction expressed by chemical formula (i). Then, by the dehydrating condensation reaction expressed by chemical formula (ii), silicon polymer having an appropriate molecular weight is produced from the silanol as an intermediate. The silicon polymer adheres to a surface of an object to be processed and is fluidized to realize a planarized film formed on the substrate surface. Thereafter, as expressed by chemical formula (iii), the silicon polymer also dehydrates to produce SiO 2  and thus SiO 2  film is formed on the substrate surface. 
     However, in the reactions in the above plasma CVD system, since a chemical reaction is caused by electrons of several eV, the molecules of the raw material gases are decomposed into many kinds of molecules. This practically makes it difficult to selectively cause only the above desired reactions. 
     In forming a SiO 2  film by reaction between TEOS and H 2 O, it is important to produce silanol by reacting TEOS, the molecular structure of which is kept intact, with H 2 O maintained at high temperature. 
     However, while the decomposition of the new material gases by plasma partially excites reaction (i), Si and SiO produced by decomposition of TEOS directly reacts with O produced by decomposition of H 2 O, for example, causing a reaction dominantly producing SiO 2 , rather than silanol, as the intermediate. Thus, it is not practically ensured that the films formed are adequately planarized by silicon polymer. 
     Furthermore, in the above plasma CVD system, since silanol is less produced and SiO 2  in gas phase dominantly adheres to the substrate surface, flatness of the films cannot be achieved without keeping the substrate at a low temperature of at most 120° C. and restraining the dehydrating condensation rate of the silanol. 
     Thus, since a SiO 2  film thus formed on a substrate maintained at low temperature has not experienced adequate reaction, it contains a large amount of OH group and has shortcomings such as large leakage current and low dielectric strength. 
     Furthermore, when heat treatment (300° C.-400° C.) is performed after the film formation to improve film quality, volumetric shrinkage is caused and thus tensile stress is caused, resulting in cracks or the like in the film. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a surface processing device and a method of processing a surface capable of precisely controlling CVD reaction to form thin films with good step coverage, which is required, for example, for manufacturing semiconductor devices. 
     Another object of the present invention is to provide a surface processing device and a method of processing a surface capable of precisely etching a surface of an object to be processed in manufacturing semiconductor devices. 
     A surface processing device according to the present invention processes a surface of an object to be processed in an atmosphere under the atmospheric pressure. It includes: a first gas supplying passage disposed near the surface of the object to be processed for supplying a first gas insusceptible to heating by electromagnetic wave; a second gas supplying passage disposed near the surface of the object to be processed for supplying a second gas susceptible to heating by electromagnetic wave; and an electromagnetic wave generating unit disposed near the surface of the object to be processed for irradiating the first gas supplied from the first gas supplying passage and the second gas supplied from the second gas supplying passage with electromagnetic wave and selectively heating only the second gas to cause reaction between the first gas and the second gas, thereby processing the surface of the object to be processed. 
     Preferably, a plurality of the first gas supplying passages and a plurality of the second gas supplying passages are alternately provided. Still preferably, the electromagnetic wave generating unit is a microwave generating unit. 
     When a gas containing TEOS is used as the first gas and a gas containing H 2 O is used as the second gas in the above surface processing device, for example, it is possible to selectively heat only the second gas, H 2 O, near the surface of the object to be processed by microwave generated from the electromagnetic wave generating unit. 
     Thus, since dissociation of molecules of the first gas, i.e., TEOS, is hardly caused, it is ensured that the following reactions are caused: 
     
       
         i) Si(OC 2 H 5 ) 4 +H 2 O→Si(OC 2 H 5 ) 4-n (OH) n +C 2 H 5 OH  (hydrolysis reaction) 
       
     
     
       
         ii) Si(OC 2 H 5 ) 4-n (OH) n →SiO m (OH) j (OC 2 H 5 ) k +H 2 O  (dehydrating condensation reaction) 
       
     
     
       
         iii) SiO 2 +H 2 O+C 2 H 5 OH 
       
     
     TEOS=Si(OC 2 H 5 ) 4    
     silanol=Si(OC 2 H 5 ) 4-n (OH) n    
     silicon polymer=SiO m (OH) j (OC 2 H 5 ) k    
     Consequently, it is ensured that silanol is produced as the intermediate and an SiO 2  film having adequate flatness can be formed. Furthermore, since the SiO 2  is continuously fired during the film formation, an SiO 2  film with small leakage current and good dielectric strength can be formed. 
     Furthermore, when a gas containing F 2  gas is used as the first gas and a gas containing H 2 O is used as the second gas, only the second gas, H 2 O, can be selectively heated by microwave generated from the electromagnetic wave generating unit, causing the following reaction without using HF vapor: 
     
       
         F 2 +H 2 O→HF+O 2 . 
       
     
     Thus, oxide films can be selectively etched safely, using HF anhydride. 
     Furthermore, the above surface processing device is provided with a gas mixing chamber for mixing the first gas supplied from the first gas supplying passage with the second gas supplied from the second gas supplying passage at the region of the outlets of the first and second gas supplying passages, the gas mixing chamber being provided with an electromagnetic wave generating unit. In this configuration, it is possible to cause the above reactions within the gas mixing chamber. 
     Still preferably, in the above surface processing device, the first and second gas supplying passages have their routes defined at their outlets by dielectric members capable of transmitting electromagnetic wave, an electromagnetic wave generating unit is provided in the region of the first and second gas supplying passages partitioned by the dielectric members, and ceramic, quarts or the like is used for the dielectric members. 
     With this structure, when there is a high reactivity between the first gas and the second gas, only the second gas can be preheated using the electromagnetic wave generating unit and thereafter the first and the second gases can be mixed to cause the above film forming and etching reactions or the like near the surface of the object to be processed. 
     A method of processing a surface according to the present invention includes, in a system including a supplying port disposed near a surface of an object to be processed for supplying a first gas insusceptible to heating by electromagnetic wave and a second gas susceptible to heating by electromagnetic wave, in an atmosphere under the atmospheric pressure, the steps of: selectively heating only the second gas by irradiating the first and second gases with electromagnetic wave; and processing the surface of the object to be processed by reaction between the first gas and the heated second gas. 
     Still preferably, the selective heating step is performed with the first gas and the second gas being separated. Still preferably, the first gas contains a first reactive gas which reacts on the second gas and the first carrier gas which does not react on the second gas, and the second gas contains a second reactive gas which reacts on the first gas and a second carrier gas which does not react on the first gas. 
     In the method of processing a surface described above, when TEOS as an organosilane compound is used as the first reactive gas, H 2 O, is used as the second reactive gas and a noble gas is used as the first and second carrier gases, only the second reactive gas, H 2 O, can be selectively heated, for example, by microwave generated from the electromagnetic wave generating unit. 
     Therefore, dissociation of molecules of the first reactive gas, TEOS, is hardly caused and thus the reactions i), ii) and iii) described above are surely performed. 
     As a result, it is ensured that silanol is produced as the intermediate and an SiO 2  film having good flatness can be formed. Furthermore, since the SiO 2  is continuously fired during the film formation, a SiO 2  film with small leakage current and good dielectric strength can be formed. 
     Furthermore, in the method of processing a surface described above, when a noble gas, such as argon and xenon, the mass numbers of which are larger than that of H 2 O, is used as the second carrier gas, energy loss due to collision of the heated H 2 O molecules is reduced so that H 2 O may not be cooled and can thus reach the reaction space near the object to be processed. 
     On the other hand, when a gas containing F 2  gas is used as the first gas and a gas containing H 2 O is used as the second gas, only the second gas, H 2 O, can be selectively heated by microwave generated from the electromagnetic wave generating unit, causing the following reaction without using HF vapor: 
     
       
         F 2 +H 2 O→HF+O 2 . 
       
     
     Thus, it is possible to selectively etch an oxide film safely, using HF anhydride. 
     Furthermore, in the above method of processing a surface, the selective heating step is performed with the first gas being separated from the second gas. 
     This allows a stable, selective heating step even when there is a high reactivity between the first gas and the second gas. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of a CVD system according to a first embodiment. 
     FIG. 2 is a perspective view of the structure of a gas separating portion. 
     FIG. 3 is a cross sectional view of a modification of the CVD system according to the first embodiment. 
     FIG. 4 is a cross sectional view of an etching system according to a second embodiment. 
     FIG. 5 is a schematic view of a structure of a conventional plasma CVD system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [First Embodiment] 
     An embodiment in which a surface processing device according to the present invention is applied to a single-wafer-processing atmospheric pressure CVD system will now be described with reference to FIGS.  1 - 3 . 
     Referring now to FIG. 1, the structure of an atmospheric pressure CVD system  100  in cross section will be described. Provided in a chamber  101  is a holder  102  which attracts a wafer  1  by evacuation and is internally provided with a heater and a cooler. Provided under holder  102  are a reactive gas lead-through port  109  and a gas reacting chamber  108 . 
     Provided under gas reacting chamber  108  are gas A supplying passages  106  for supplying a gas A insusceptible to heating by electromagnetic wave to gas reacting chamber  108  and gas B supplying passages  107  for supplying a gas B susceptible to heating by electromagnetic wave to gas reactive chamber  108  such that these supplying passages are partitioned by diaphragms  105 , thus providing a gas separating portion  104  in which gas A supplying passages  106  and gas B supplying passages  107  are alternately disposed. 
     As for the details of the structure of gas separating portion  104 , as shown in the perspective view in FIG. 2, an electromagnetic induction tube  111  is provided for introducing electromagnetic wave  500  radiating from an electromagnetic wave generating unit  103  to gas reacting chamber  108 , and the dimensions of gas separating portion  104  according to the present invention are approximately L=at most 40 cm, W=at most 40 cm and H=at most 10 cm. 
     Preferably, the distance (S) between wafer  1  and gas reacting camber  108  is approximately 3 mm. 
     Furthermore, when there is a high reactivity between gas A and gas B, it is effective to use an atmospheric pressure CVD system  150  shown in FIG.  3 . 
     Atmospheric pressure CVD system  150  shown in FIG. 3 has the same structure as atmospheric pressure CVD system  100  shown in FIG. 1, except for the structure of gas reacting chamber  108 . 
     In gas reacting chamber  108  of atmospheric pressure CVD system  150 , gas A supplying passages  106  and gas B supplying passages  107  are also provided such that these passages are partitioned by dielectric diaphragms. 
     Dielectric diaphragms  112  are formed of a material capable of transmitting electromagnetic wave generated from electromagnetic wave generating unit  103 , such as quarts or ceramic. 
     Thus, in this structure, gas A is not mixed with gas B in gas reacting chamber  108 , only gas B is selectively heated by electromagnetic wave  200  radiating from electromagnetic wave generating unit  103 , and gas A will not react with gas B until they reach reactive gas lead-through port  109 . 
     Both atmospheric pressure CVD systems  100  and  150  shown in FIGS. 1 and 3, respectively, are provided with a gas exhaust passage  114  above holder  102  for exhausting gas. 
     An example of SiO 2  film formation onto wafer  1  using atmospheric pressure CVD system  100  or  150  will now be described. 
     The conditions of gas A, gas B and atmospheric pressure CVD system  100  are as follows: 
     Gas A 
     First reactive gas: TEOS (tetraethoxysilane) with a flow rate of 0.5 SLM (Standard Liter per Minute) 
     First carrier gas: Xe with a flow rate of 5.0 SLM 
     Gas B 
     Second reactive gas: H 2 O with a flow rate of 1.0 SLM 
     Second carrier gas: Xe with a flow rate of 5.0 SLM 
     Electromagnetic Wave 
     Microwave with a microwave power of 200 W 
     Temperature of holder: 350° C. 
     When gas A reacts with gas B under the above conditions, the following reactions are caused: 
     
       
         i) Si(OC 2 H 5 ) 4 +H 2 O→Si(OC 2 H 5 ) 4-n (OH) n +C 2 H 5 OH  (hydrolysis reaction) 
       
     
     
       
         ii) Si(OC 2 H 5 ) 4-n (OH) n →SiO m (OH) j (OC 2 H 5 ) k +H 2 O  (dehydrating condensation reaction) 
       
     
     
       
         iii) SiO 2 +H 2 O+C 2 H 5 OH 
       
     
     TEOS=Si(OC 2 H 5 ) 4    
     silanol=Si(OC 2 H 5 ) 4-n (OH) n    
     silicon polymer=SiO m (OH) j (OC 2 H 5 ) k    
     The characteristics of the film formed, when the film thickness=0.1 μm and the electric field applied=6 MV/cm are as follows wherein the term “BHF” denotes buffered hydrofluoric acid, i.e., an aqueous solution of a mixture of hydrogen fluoride (HF) and ammonium fluoride (NF 4 F): 
     Growth rate of SiO 2 : 0.5 μm/min 
     Flatness: ±2% 
     Film quality: refractive index n=1.50 
     Film stress (tension): 0.5×10 9  dyn/cm 2    
     6:3 BHF (etching rate): 0.12 μm/min 
     Breakdown electric field: 9.5 MV/cm 
     Leakage current: 200 pA/cm 2    
     The reason why only gas B, H 2 O, is heated by microwave while the temperature of TEOS is not increased in reacting H 2 O with TEOS is as follows: in order to provide adequate reactivity to H 2 O, the temperature of H 2 O need be increased to at least 600° C. On the other hand, when the temperature of TEOS is increased to at least 500° C., the following reaction proceeds by pyrolysis reaction: 
     
       
         Si(OC 2 H 5 ) 4 →SiO 2 +C 2 H 5 ·OH. 
       
     
     In other words, when the temperature of TEOS is increased, the reaction to produce SiO 2  proceeds in gas phase so that the reaction to produce silanol, which is essential to planarizing the film, is restrained. Furthermore, the composition of SiO 2  at the film surface, which should be mainly composed of silanol polymer, includes SiO 2  in solid phase, resulting in degradation in fluidity and hence in flatness. 
     Therefore, in order to obtain adequate flatness, it is important that the temperature of H 2 O only is increased while that of TEOS is not increased. 
     The reason why H 2 O is heated by microwave is as follows: in order to heat only H 2 O while TEOS is not heated, gas introducing paths of gas A and gas B may be separated from each other, for example, so that H 2 O can be heated at the H 2 O introducing path. However, when the heating portion is distant from the wafer surface and the wafer surface is maintained at low temperature, the heated H 2 O is cooled between the wafer surface and the H 2 O heating portion and the temperature of H 2 O required at the wafer surface cannot be obtained. 
     In order to avoid this, the entire H 2 O gas passages up to the wafer surface may be maintained at high temperature. However, this allows the temperature of TEOS introduced onto the wafer surface to increase and the requirement that only H 2 O is heated cannot be satisfied. 
     Furthermore, the temperature of a wafer surface can be determined by the characteristic of the film formed on the wafer. For example, the temperature of the wafer surface must not exceed 450° C. in forming films in the process for aluminum multilayer interconnections. 
     Thus, heating by microwave is considered to be optimal as a method of only increasing the temperature of H 2 O at or near the wafer surface. 
     In the present embodiment, as described above, since the temperature of H 2 O only is increased to 600° C.-800° C. using microwave, dissociation of TEOS molecules is hardly caused and thus the formation reaction of the silanol required is adequately caused. Thus, an SiO 2  film with a superior flatness can be formed as compared with those conventionally formed. 
     Furthermore, since silanol is selectively formed to form an SiO 2  film and thus there is nothing to prevent flow of the silanol contained in the film being formed, the surface of the film being formed is mainly formed of polymer having a molecular weight which allows flow of the polymer even when the dehydrating condensation weight at the wafer is increased. Thus, enhanced flatness can be realized under a film forming condition of a temperature of 300° C.-400° C. Furthermore, since the SiO 2  film is continuously fired at a temperature of as high as 300° C.-400° C. during the forming of the SiO 2  film, a film with small leakage current and good dielectric strength can be formed with low stress. 
     While an example in which TEOS is used as the first reactive gas has been described, the silane compound and the organosilane compounds shown in Table 1 may be used to obtain a similar effect. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 silane 
                 SiH 4   
                 silane 
               
               
                 compound 
                 Si 2 H 6   
                 disilane 
               
               
                   
                 Si 3 H 8   
                 trisilane 
               
               
                   
                 Si 2 H 2 Cl 2   
                 dichlorosilane 
               
               
                 organosilane 
                 Si(OC 2 H 5 ) 4   
                 TEOS 
               
               
                 compound 
                 Si(OCH 3 ) 4   
                 tetraethoxysilane 
               
               
                   
                   
                 TMOS 
               
               
                   
                   
                 tetramethoxy 
               
               
                   
                   
                 silane 
               
               
                   
                 Si(OCH 3 ) 2 (OC 4 H 9 ) 2   
                 DADBS 
               
               
                   
                   
                 diacetoxydibutoxy 
               
               
                   
                   
                 silane 
               
               
                   
               
               
                   
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 HMDS hexamethyl disiloxane 
               
               
                   
               
               
                   
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 HEDS hexaethyl disiloxane 
               
               
                   
               
               
                   
                 Si(OC 2 H 5 ) 3 H 
                 triethoxysilane 
               
               
                   
               
               
                   
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 TMCTS tetramethylcyclo trisiloxane 
               
               
                   
               
             
          
         
       
     
     Furthermore, while Xe has been used as the second carrier gas for H 2 O, N 2  (the mass number=28) is often used as a carrier gas for H 2 O in a conventional CVD system. H 2 O molecules heated by microwave, when colliding against the carrier gas molecules, will lose their energy and thus the H 2 O molecules are cooled. However, it is physically apparent that when H 2 O molecules collide against molecules having a relatively larger mass number, the H 2 O molecules lose less energy per one collision, and thus are hard to cool. 
     Thus, if a gas having a mass number larger than that of H 2 O, 18, is used as the carrier gas, the heated H 2 O molecules are not cooled and thus reach the reaction space so that the heating of H 2 O by microwave is effectively used. Thus, while Xe having a mass number of 131 has been used in the present embodiment, Ar having a mass number of 40 can also be used. 
     Furthermore, while a signal-wafer-processing atmospheric pressure CVD system is used in the first embodiment, a batch-processing CVD system or a CVD system which continuously processes wafers may be used to obtain similar function and effect. 
     [Second Embodiment] 
     An example in which a surface processing device according to the present invention is applied to an etching system will now be described with reference to FIG.  4 . FIG. 4 shows the structure of an etching system  250  in cross section. 
     Provided within a chamber  201  is a holder  202  which supports a wafer  1 . Provided above holder  202  are a reactive gas lead-through port  213  and a gas reacting chamber  208 . 
     Provided above gas reacting chamber  208  are gas A supplying passages  206  for supplying a gas A insusceptible to heating by electromagnetic wave to gas reacting chamber  208  and gas B supplying passages  207  for supplying a gas B susceptible to heating by electromagnetic wave to gas reacting chamber  208  such that these passages are partitioned by diaphragms  205 , thus providing a gas separating portion  204  with gas A supplying passages  206  and gas B supplying passages  207  alternately disposed. 
     In etching system  250  also, gas A supplying passages  206  and gas B supplying passages  207  are partitioned up to reactive gas lead-through port  213  by diaphragms  212  formed of a dielectric material within gas reacting chamber  208 , and an electromagnetic wave generating unit  203  for radiating electromagnetic wave  200  is provided at gas reacting chamber  208 . Dielectric diaphragms  212  are formed of quarts, ceramic or the like. 
     Provided below chamber  201  is a removal unit  215  for externally exhausting the gas sent from gas A supplying passages  206  and gas B supplying passages  207 . 
     In the above etching system  250  also, gas B can be selectively heated in gas reacting chamber  208  by irradiating gas A and gas B with electromagnetic wave  200 . 
     A specific example in which the above etching system  250  is used to etch an oxide film on a surface of wafer  1  will now be described. 
     The conditions of gas A, gas B and etching system  250  are as follows: 
     Gas A: F 2  with a flow rate of 1.0 SLM 
     Gas B: H 2 O with a flow rate of 0.1 SLM 
     Electromagnetic Wave: microwave with a microwave power of 20 W 
     Temperature of wafer: 100° C. 
     When gas A reacts with gas B under the above conditions, the following reaction is caused: 
     
       
         F 2 +H 2 O→HF+O 2 . 
       
     
     The result of the etching is as follows: the etching rate is 1.0 μm/min for a BPSG film and 0.01 μm/min for a thermal oxide film. 
     Thus, selective etching of oxide films by using HF anhydride can be applied. Since oxide films can be selectively etched without using HF vapor, the gas introducing passages need not be corrosion-resistant. This allows safe, selective etching of oxide films. 
     The reason why the temperature of H 2 O only is increased while that of F 2  is not increased is that the above reaction fails to materialize when the temperature of H 2 O is low and that the above reaction materializes when the temperature of H 2 O is at least 400° C. 
     On the other hand, when the temperature of F 2  is increased, F radicals are produced and the pipes for the gas introduction system are undesirably eroded. 
     Thus, it becomes possible to cause the above reaction safely by selectively increasing the temperature of H 2 O. 
     In a surface processing device according to the present invention, when a gas containing TEOS is used as the first gas and a gas containing H 2 O is used as the second gas, only the second gas, H 2 O, can be selectively heated near a surface of an object to be processed by microwave generated from an electromagnetic wave generating unit. Consequently, since dissociation of molecules of the first gas, TEOS, is hardly caused, it is ensured that silanol is produced as an intermediate and thus an SiO 2  film having good flatness can be formed. Furthermore, since the SiO 2  is continuously fired during the film formation, a SiO 2  film with small leakage current and good dielectric strength can be formed. 
     Furthermore, when a gas containing F 2  gas is used as the first gas and a gas containing H 2 O is used as the second gas, only the second gas, H 2 O, can be selectively heated by microwave generated from the electromagnetic wave generating unit, allowing selective etching of oxide films using HF anhydride rather than HF vapor. 
     In the method of processing a surface according to the present invention, when TEOS as an organosilane compound is used as the first reactive gas, H 2 O is used as the second reactive gas and a noble gas is used as the first and second carrier gases, only the second reactive gas, H 2 O, can be selectively heated, for example, by microwave generated from the electromagnetic wave generating unit. Consequently, since dissociation of molecules of the first reactive gas, TEOS, is hardly caused, it is ensured that silanol is produced as an intermediate and thus a SiO 2  film having good flatness can be formed. Furthermore, since the SiO 2  is continuously fired during the film formation, a SiO 2  film with small leakage current and good dielectric strength can be formed. 
     Furthermore, in the above method of processing a surface, a noble gas such as argon, xenon or the like having a mass number larger than that of H 2 O may be used as the second carrier gas so that energy loss of the heated H 2 O molecules due to collision against molecules of the noble gas can be reduced and thus the H 2 O molecules, without being cooled, can reach the reaction space near the object to be processed. 
     On the other hand, when a gas containing F 2  gas is used as the first gas and a gas containing H 2 O is used as the second gas, the second gas, H 2 O, can be selectively heated by microwave generated by the electromagnetic wave generating unit, allowing selective etching of oxide films using HF anhydride rather than HF vapor. 
     Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.