Abstract:
A surface processing apparatus includes a process chamber including a gas ejection mechanism; an exhaust for exhausting the inside of said process chamber; and a gas supply for supplying a gas to the gas ejection mechanism. The gas ejection mechanism includes a first gas distribution mechanism for distributing the gas into a cooling or heating mechanism, including a gas distribution plate placed in the frame member, the gas distribution plate having a plurality of holes that extend therethrough, the cooling or heating mechanism having multiple gas passages that extend therethrough, the plate having a number of outlets to eject the gas into the process chamber, wherein there are more outlets in the plate than there are gas passages, and the plate is fixed to a second gas distribution mechanism with a clamping member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. Ser. No. 11/845,135, filed on Aug. 27, 2007, which is a continuation of U.S. Ser. No. 10/234,540, filed on Sep. 5, 2002, and which claims the priority of Japanese Patent Application No. 2001-273027, filed in Japan on Sep. 10, 2001. The contents of U.S. Ser. No. 10/234,540; U.S. Ser. No. 11/845,135; and Japanese Patent Application No. 2001-273027 are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a surface processing apparatus and, more particularly, to a surface processing apparatus with a gas ejection mechanism, which has an excellent uniformity in temperature over the entire surface, and suppresses the temperature change during processing. 
         [0004]    2. Related Art 
         [0005]    The surface processing carried out using gas, such as a dry etching and CVD, is greatly influenced by the temperature of a substrate and members surrounding the substrate, and the flow of gas. Therefore, in order to carry out stable processing continuously, a gas ejection mechanism which is controlled to make gas uniformly flow and is maintained at a prescribed temperature is required as well as a mechanism to control the substrate temperature. 
         [0006]    A conventional gas ejection mechanism is explained with reference to  FIG. 11 .  FIG. 11  is a cross sectional view showing the configuration of a dry etching apparatus disclosed in JP7-335635A. 
         [0007]    As shown in the drawing, a gas ejection mechanism  101 , which serves as an opposite electrode, is arranged facing a substrate  105  in a process chamber  100 . The opposite electrode  101 , composed of a gas diffusion plate  104  having a number of gas outlets  104   a , a support plate holding this gas diffusion plate, and a cooling jacket  102  having a coolant channel  106  inside, is fixed to process chamber  100  through an insulator  108 . Gas passages  102   a  and  103   a  are respectively provided in cooling jacket  102  and support plate  103  so that the passages are communicated with gas outlets  104   a  of the gas diffusion plate. The gas diffusion plate  104  is fixed with, for example, brazing on support plate  103  of about 10 mm in thickness. The support plate is further fixed on cooling jacket  102  with bolts  109 . In addition, gas distribution grooves  103   b  and  104   b  are formed perpendicularly on the contact surfaces of the support plate and the gas diffusion plate to easily align gas outlets  104   a  and gas passages  103   a . The gas that is introduced through a gas introduction pipe  110  is distributed in a gas passage  107  and then is ejected into process chamber  100  from gas outlets  104   a  through gas passages  102   a ,  103   a  and gas distribution grooves  103   b ,  104   b.    
         [0008]    The cooling water channel  106  is formed in cooling jacket  102 . The cooling water is supplied from a cooling water supply pipe  106   a  and drained into discharge pipe  106   b . The gas diffusion plate exposed to plasma is indirectly cooled through the heat transfer between the cooling jacket and support plate and then between the support plate and the gas diffusion plate. Thus, the temperature rise of gas diffusion plate is prevented to carry out uniform etching processing. 
         [0009]    During the research and developments of the high-speed etching technique for ultra-fine patterns, the present inventors studied the relations between the configuration of the gas ejection mechanism and the accuracy of etched pattern, and found that more uniform gas flow and more precise control of gas diffusion plate temperature are required in order to carry out finer pattern etching. However, it was practically impossible to simultaneously satisfy both conditions as long as the gas ejection mechanism shown in  FIG. 11  is employed. 
         [0010]    That is, since the gas diffusion plate was indirectly cooled through the support plate as shown in  FIG. 11 , the capacity to cool the gas diffusion plate was insufficient for some processing conditions, and the etching uniformity was decreased as the etching pattern became finer. Then, the present inventors enlarged the cooling water channel in order to improve cooling capacity; however, the density of gas outlets had to be reduced, which decreased the uniformity of gas flow diffusion and resulted in insufficient etching uniformity. 
         [0011]    Furthermore, when processing is repeatedly and continuously carried out, the desired etching characteristic cannot be obtained during a period after the processing starts. That is, the processing is made in vain during this period. This problem becomes more serious as the etching pattern becomes finer. In the case of, e.g., 0.13 pm pattern, the desired characteristic was not obtained for first fifteen to twenty wafers after the processing started. 
         [0012]    The gas ejection mechanism of  FIG. 11  is constructed by fixing the gas diffusion plate on the support plate with, e.g., brazing. Therefore, the surface of gas diffusion plate is easily contaminated to deteriorate the etching characteristic. In addition, it is not easy to fix the gas diffusion plate without clogging gas outlets. This work is complicated and requires high skill and time. The method of fixing the gas diffusion plate by fastening parts of gas diffusion plate with bolts is also disclosed. However, sufficient cooling effect could not be obtained and the gas diffusion plate was difficult to be evenly pressed, resulting in large non-uniform temperature distribution. Furthermore, This method is disadvantageous in that the gas diffusion plate is easy to break down by heat during processing. 
         [0013]    Furthermore, although the gas diffusion plate is preferably made from scavenger materials in order to remove the activated species which reacts with photoresist, such materials as Si or SiO 2  has a disadvantage of being easily broken due to thermal hysteresis if a complicated shape such as groove is formed. 
         [0014]    The problems as to the gas flow diffusion and the temperature distribution of the gas diffusion plate are also observed in the cases of other surface processing apparatuses. For example, if the gas ejection mechanism of thermal CVD apparatus has a non-uniform temperature distribution, the decomposition of gas and film deposition occurs more rapidly at higher temperature portions. The deposited film will peel off and cause the generation of particles. In addition, the film deposition rate varies with the position on the substrate depending on the temperature distribution of the gas diffusion plate under certain circumstances. 
       SUMMARY 
       [0015]    The present inventors have further made examinations especially on etching apparatuses based on above-mentioned information. That is, the inventors have earnestly studied the relationship among the structure of the gas ejection mechanism, the arrangement of its constituting members, etching characteristic and reproducibility, and finally completed this invention. 
         [0016]    An object of this invention is to realize a gas ejection mechanism, which makes it possible to form a uniform gas flow diffusion and to control the temperature and its distribution of a gas diffusion plate, and then to provide a surface processing apparatus, which can continuously carry out uniform processing. 
         [0017]    A first surface processing apparatus embodiment of this invention comprises a surface processing apparatus including a process chamber in which a substrate holding mechanism holding a substrate and a gas ejection mechanism are arranged to face each other; an exhaust for exhausting the inside of said process chamber; and a gas supply for supplying a gas to the gas ejection mechanism to process the substrate with the gas introduced into said process chamber through said gas ejection mechanism. The gas ejection mechanism includes a frame member, a cooling or heating mechanism, a first gas diffusion mechanism for distributing the gas into the cooling or heating mechanism, the cooling or heating mechanism including a gas diffusion plate placed in the frame member, the gas diffusion plate having a plurality of holes that extend therethrough, the cooling or heating mechanism including a coolant or heating channel to cool or heat a plate that is exposed in the process chamber, the cooling or heating mechanism having multiple gas passages that extend therethrough, the exposed plate having a number of outlets to eject the gas into the process chamber, wherein there are more outlets in the exposed plate than there are gas passages, the exposed plate fixed to a second gas diffusion mechanism with a clamping member, and the second gas diffusion mechanism having a space that is disposed between the cooling or heating mechanism and the exposed plate, wherein all of the gas passages of the cooling or heating mechanism open into the space, and the space extends over all of the outlets of the exposed plate, whereby the gas supplied from the gas supply passes through in the order of the first gas diffusion mechanism, the cooling or heating mechanism, the second gas diffusion mechanism, and the exposed plate to be ejected from the outlets of the plate into the process chamber. 
         [0018]    Thus, a uniform gas flow diffusion can be formed by arranging a gas ejection mechanism, a cooling or a heating mechanism, and a gas diffusion plate in this order from the upper stream to construct a gas ejection mechanism. In addition, since the gas diffusion plate is in direct contact with the heating or cooling mechanism and evenly pressed by an electrostatic chucking mechanism or a clamping mechanism, the efficiency to cool or heat the gas diffusion plate and its uniformity are remarkably improved, and therefore the gas diffusion plate surface can be maintained at a predetermined temperature uniformly over the whole surface. 
         [0019]    A second surface processing apparatus embodiment of this invention comprises a process chamber in which a substrate holding mechanism holding substrate and a gas ejection mechanism are arranged to face each other; an exhaust for exhausting the inside of said process chamber; and a gas supply for supplying a gas to the gas ejection mechanism to process the substrate with the gas introduced into said process chamber through said gas ejection mechanism. The said gas ejection mechanism comprising a frame member, a cooling or heating mechanism, a first gas diffusion mechanism for distributing the gas flowing into the cooling or heating mechanism, the first gas diffusion mechanism including a gas diffusion plate placed in the frame member, the gas diffusion plate having a plurality of holes that extend therethrough, the cooling or heating mechanism including a coolant or heating channel to cool or heat a plate that is exposed in the process chamber, the cooling or heating mechanism having multiple gas passages that extend therethrough, the exposed plate having a number of outlets to eject the gas into the process chamber, the exposed plate fixed to a second gas diffusion mechanism with a clamping member, and the second gas distributing mechanism arranged between the cooling or heating mechanism and the exposed plate, whereby the gas supplied from the gas supply passes through, in the order of, the first gas diffusion mechanism, the cooling or heating mechanism, the second gas diffusion mechanism, and the plate to be ejected from the outlets into the process chamber. 
         [0020]    In one version, there are more outlets in the exposed plate than there are gas passages. In another version, the second gas distributing mechanism has the same number of inlets for the gas as that of gas passages and has the same number of outlets as that of outlets of the exposed plate. 
         [0021]    By arranging a second gas diffusion mechanism between a gas diffusion plate and a cooling or a heating mechanism, and by branching gas passages of the cooling or heating mechanism, the gas outlets can be formed just under, e.g., a coolant channel. That is, even if a coolant channel with large cooling capacity is provided, a large number of gas outlets can be formed with high density, which is inevitable for forming a uniform gas flow diffusion. Consequently, as in the case of the first surface processing apparatus mentioned above, it becomes possible to form uniform gas flow diffusion, to prevent the temperature rise of the gas diffusion plate and to improve the temperature uniformity. Thus, uniform processing can be made stably and repeatedly. 
         [0022]    The second gas diffusion mechanism is preferable to be a space with a height of 0.1 mm or less and the pressure in this space is set to 100 Pa or higher. Thereby, the heat transfer between the cooling or heating mechanism and the gas diffusion plate with gas is increased, which improves the cooling efficiency. Furthermore, the diameter of gas outlet of 0.01-1 mm is desirable, and that of 0.2 mm or less is preferable, which can control gas flow diffusion more uniformly and eject gas uniformly over the whole substrate. 
         [0023]    The surface processing apparatus is preferably applied to a plasma processing apparatus, which carries out processing by supplying high frequency electric power to the gas ejection mechanism to generate plasma. 
         [0024]    Moreover, the efficiency for cooling or heating the gas diffusion plate, and the temperature uniformity of the gas diffusion plate are further improved by preparing the ruggedness on both surfaces of the gas diffusion plate and the cooling or heating mechanism or both surfaces of the gas diffusion plate and the second gas diffusion mechanism so that the ruggedness of both surfaces is engaged with each other. 
         [0025]    A flexible heat conductive sheet may be sandwiched between the gas diffusion plate and the cooling or heating mechanism or between the gas diffusion plate and the second gas diffusion mechanism. The heat conductive sheet enters into the microscopic roughness, which improves the heat transfer between them. 
         [0026]    As a material of the gas diffusion plate, non-metal material such as Si, Si02, SiC, carbon, or the like is preferably used, especially for an etching apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a cross-sectional view showing a first embodiment of this invention. 
           [0028]      FIG. 2  is a cross-sectional view showing an example of a gas diffusion plate clamping mechanism of this invention. 
           [0029]      FIGS. 3-5 ,  7 - 8  show a cross-sectional view of an example of gas ejection mechanism. 
           [0030]      FIG. 6  is a cross-sectional view showing a second embodiment of this invention. 
           [0031]      FIG. 9  is a cross-sectional view showing a third embodiment of this invention. 
           [0032]      FIG. 10  is a sectional-sectional view showing a fourth embodiment of this invention. 
           [0033]      FIG. 11  is a cross-sectional view showing a gas ejection mechanism of the conventional etching apparatus. 
       
    
    
       [0034]    In these drawings, numeral  1  denotes a process chamber;  2 , a gas ejection mechanisms (opposite electrode);  3 , a frame member;  4 , a gas diffusion mechanism (a gas diffusion space);  4   a , a gas diffusion plate;  5 , cooling jacket;  5   a , a gas passage;  5   b , a coolant channel:  6 , a gas diffusion plate;  6   a , a gas outlet;  7 , a substrate holding electrode (substrate holding mechanism);  8 , a coolant channel;  9 , an electrostatic chuck;  10 , a gas introduction pipe;  11 , a second gas diffusion mechanism (a second gas diffusion space);  12   a ,  12   b , an insulator;  13 , a valve;  14 ,  15 ; a high frequency power source;  17 , a DC power source;  19 , an ejector pin;  21 , a bellows;  22 , a gas supply system;  24 , an annular fastener;  25 , a screw;  26 , heat conductive sheet;  27 , an electrostatic chuck;  27   a , a dipole electrode;  29 , ruggedness;  31 , a gas branch groove (passage);  32 , a heating mechanism;  32   b ,  33 . a heater;  40 , substrate;  41 ,  43  O-ring;  42 , passage;  44 , connecting member,  45 , pressure gauge; and  46 , insulator. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    The preferred embodiments of this invention will be explained with reference to drawings. 
         [0036]    An etching apparatus, one of surface processing apparatuses of this invention, is explained below as the first embodiment.  FIG. 1  is a cross sectional view showing an example of etching apparatuses of this invention, which carries out the etching processing on a substrate by ejecting a process gas toward the substrate from a gas ejection mechanism and supplying high frequency electric power to the gas ejection mechanism to generate plasma. That is, in this embodiment, the gas ejection mechanism plays a role of an opposite electrode, which is arranged facing a substrate holding electrode. 
         [0037]    As shown in  FIG. 1 , opposite electrode (gas ejection mechanism)  2  and substrate holding electrode (substrate holding mechanism)  7  which holds a substrate  40  are arranged facing each other in a process chamber  1 , and are fixed to the process chamber  1  through insulators  12   a  and  12   b , respectively. 
         [0038]    The process chamber is connected with an exhaust means (not illustrated) through a valve  13 . The opposite electrode  2  is connected with a first high frequency power source  14  for generating plasma as well as with a gas supply means  22  which is composed of a gas cylinder, a mass flow controller, a stop valve and the like through a gas introduction pipe  10 . 
         [0039]    The opposite electrode  2  comprises: a gas diffusion mechanism; a cooling jacket (cooling mechanism)  5  having a number of gas passages  5   a ; and a gas diffusion plate  6  having a number of gas outlets  6   a  which are communicated with gas passages  5   a . These are placed in and fixed to a cylindrical frame body  3 . A coolant channel Sb is formed in cooling jacket  5 . A coolant is supplied from an introduction pipe  5   c  to coolant channel  5   b  through a pipe installed in, e.g., frame  3 , and is discharged through a discharge pipe  5   d . Here, the gas diffusion mechanism which is provided with one or more gas diffusion plates  4   a  having a number of small holes is preferably employed. 
         [0040]      FIG. 2  is an enlarged view showing a fixing method of gas diffusion plate  6 , where gas diffusion plate  6  directly comes in contact with cooling jacket  5  and is fixed by a clamping mechanism, which is composed of an annular fastener  24  and screws  25 . Such clamping mechanism enables it to fix gas diffusion plate  6  all around. The gas diffusion plate  6  can be pressed and fixed uniformly to cooling jacket  5  with higher pressure, unlike the prior art where the gas diffusion plate is fixed by pressing parts of gas diffusion plate with tightening screws. Thus, this improves the cooling efficiency as a result of the increase in heat transfer, and avoids breakage of gas diffusion plate  6  when pressed. It is also possible to avoid the deterioration of etching processing characteristic due to the impurity contamination and the clogging of gas outlets, which often takes place when a brazing or adhesive is used for fixing. 
         [0041]    The process gas that is supplied to the opposite electrode through gas introduction pipe  10  flows through small holes of gas diffusion plate  4  to spread uniformly insides the gas diffusion mechanism, then passes through gas passages  5   a  of cooling jacket  5 , and flows out of gas outlets of gas diffusion plate  6  to the inside of process chamber  1 . 
         [0042]    As mentioned above, gas diffusion plate  4   a , cooling jacket  5 , and gas diffusion plate  6  are arranged in this order from the upper stream to construct the opposite electrode. Furthermore, gas diffusion plate  6  is in direct contact with cooling jacket  5  and is pressed to be fixed with uniform force. This configuration enables it to make process gas uniformly flow towards substrate  40  and cool gas diffusion plate  6  efficiently and uniformly. 
         [0043]    That is, since the process gas flows out uniformly toward the substrate from a number of gas outlets of the gas diffusion plate, the concentration of activated species which etches a substrate surface becomes uniform, making the etching rate and the shape of contact holes uniform over the whole substrate surface. Moreover, even for the processing conditions in which high RF electric power is supplied to opposite electrode  2  or substrate holding electrode  7 , it is possible to effectively suppress the temperature rise of gas diffusion plate, and to prevent the decrease in etching rate due to the deposition of substances having a low melting point on substrate and the etching failure of contact holes or the like. 
         [0044]    There is installed substrate holding electrode  7  on which an electrostatic chuck  9  is installed and in which a coolant channel  8  is provided. A coolant is introduced through introduction pipe  8   a , and is discharged through exhaust pipe  8   b . The substrate is cooled to a predetermined temperature with this coolant through the electrostatic chuck. The substrate holding electrode  7  is connected to a second high frequency power source  15  for bias control of substrate, and a DC power source  17  for substrate electrostatic chucking. Between the power sources and substrate holding electrode  7 , a blocking condenser  16  and a high frequency cut filter  18  are installed to prevent the mutual interaction between two power sources. 
         [0045]    Furthermore, holes  20  are formed in substrate holding electrode  7 . Ejector pins  19  are mounted inside the holes to move a substrate up and down when the substrate is transferred. The inside of hole is separated from the atmosphere with a bellows  21  and a plate  21   a . The ejector pin  19  is fixed on plate  21   a.    
         [0046]    The etching processing using the apparatus of  FIG. 1  is carried out as follows. The plate  21   a  of bellows  21  is pushed up with a driving mechanism to lift ejector pins  19  up. In this state, a robot hand holding a substrate is inserted through a gate valve (not illustrated) to place the substrate on ejector pins  19 . The pins are moved down to place substrate  40  on electrostatic chuck  9 , and then a predetermined electrical voltage is applied from DC power source  17  to electrostatically chuck the substrate. 
         [0047]    Subsequently, process gas is supplied into process chamber  1  from the gas supply system  22  through the gas introduction pipe  10  and opposite electrode  2 , and the pressure is set at a predetermined value. The high frequency electric powers of VHF band (for example, 60 MHz) and of HF band (for example, 1.6 MHz) are fed to opposite electrode  2  and substrate holding electrode  7  from first and second high frequency power sources  14 ,  15 , respectively. 
         [0048]    The high-density plasma is generated by the high frequency electric power of VHF band, producing activated species, which etches substrate surface. In constract, the energy of ions is controlled independently of plasma density by the high frequency electric power of HF band. That is, any etching characteristic may be obtained by appropriately selecting two high frequency electric powers. 
         [0049]    When such etching processing is repeatedly carried out, the temperature of the gas diffusion plate will gradually increase to equilibrium and the etched pattern will also vary, as mentioned above. However, since the efficiency to cool the gas ejection mechanism is improved in this embodiment, the number of processing can be reduced till the gas diffusion plate reaches thermal equilibrium. For example, in the case of 0.13 pm pattern, the number of processing was about 10 times until the stable etching characteristic was obtained after the processing started. Moreover, the temperature distribution of the gas diffusion plate became more uniform, improving the uniformities of etching rate and contact hole configuration over the whole substrate. 
         [0050]    That is, by employing the apparatus shown in  FIG. 1 , it becomes possible to accomplish simultaneously both the uniform gas flow diffusion and the efficient cooling of the gas diffusion plate, which enables it to carry out etching processing of finer pattern with stability and high productivity. 
         [0051]    In this invention, the gas outlet of 0.01-1 mm in diameter is desirable, and that of 0.2 mm or less is preferable. In this range, it is easier to control the gas flow diffusion and eject gas more uniformly out of gas outlets. The thickness of the gas diffusion plate is usually 1.0-15.0 mm. 
         [0052]    Moreover, the positions of gas passage  5   a  of the cooling jacket and gas outlet  6   a  of the gas diffusion plate may be deviated from each other to decrease the conductance, whereby the flow rate is reduced and the plasma is restrained from penetrating into the electrode. This method is preferably adopted when it is difficult to form small holes in the gas diffusion plate. The hole size of gas passage is usually 1.0-3.0 mm. 
         [0053]    The diameter of holes of gas diffusion plate  4   a  is 0.1-3.0 mm. Here, the diameter and the number (density) of holes are preferably selected so as to make the pressure gradient small over the whole gas diffusion plate and be suited to this gradient, whereby more uniform gas ejection can be realized. 
         [0054]    Next, other examples of this embodiment are shown in  FIGS. 3-5 . 
         [0055]    The gas diffusion plate  6  and cooling jacket  5  are in direct contact with each other in  FIG. 1 . However, a heat conductive sheet, which is flexible and highly heat conductive, may be placed between them as shown in  FIG. 3 . By placing such a heat conductive sheet, the sheet enters into microscopic roughness by pressure to increase the substantial contact area and improve the heat transfer rate. A sheet with a thickness of 10-500 pm of metal such as indium or polymer such as silicon resin and conductive rubber is used for the heat conductive sheet. 
         [0056]    An electrostatic chucking mechanism is installed in  FIG. 4  instead of the gas diffusion plate clamping mechanism of  FIG. 1 . Here, electrostatic chuck  27  constructed by arranging dipole electrodes  27   a  in a dielectric is installed on cooling jacket  5 . A predetermined voltage is applied to dipole electrodes  27   a  from a power source  28  to electrostatically chuck the gas diffusion plate. Since the whole gas diffusion plate can be uniformly pressed by using the electrostatic chuck, the cooling efficiency and its uniformity are further improved. Moreover, it is easier to exchange the gas diffusion plate. Any type of electrostatic chuck can be also used other than those with the dipole electrodes. 
         [0057]    On both surfaces of gas diffusion plate  6  and cooling jacket  5  of the gas ejection mechanism shown in  FIG. 5 , there is formed the ruggedness  29  that is engaged with each other to increase contact area and to improve the heat conduction. The engagement of ruggedness prevents the gas diffusion plate from bending even when the gas diffusion plate is partially heated to bend. The bending stress works to increase the contact area and the pressure at the engaged portions, which increases the heat transfer. Therefore, it is possible to prevent the prior art disadvantage, in which gaps are generated due to the bend of gas diffusion plate and as a result the temperature thereof further rises to decrease the temperature uniformity. 
         [0058]    In the above-mentioned embodiments, the gas diffusion mechanism has a configuration that one or more gas diffusion plates are installed in the space over the cooling jacket. However, the gas diffusion plate is not always required in this invention. That is, the gas diffusion mechanism where only the space is provided between the gas introduction pipe and the cooling jacket can also be employed in this invention. 
         [0059]    The second embodiment of this invention is shown in  FIG. 6 . A gas ejection mechanism of this embodiment is constructed in such a manner that first gas diffusion mechanism comprising one or more of gas diffusion plates, cooling jacket  5 , second gas diffusion mechanism  11 , and gas diffusion plate  6  are arranged in this order from the upper stream. The second diffusion mechanism is arranged in this embodiment, which is different from the first embodiment. The arrangement of the second gas diffusion mechanism between cooling jacket  5  and gas diffusion plate  6  makes it possible to enlarge the coolant channel (i.e., to increase the cooling capacity) as well as to provide gas outlets under the coolant channel Sb in order to make gas flow diffusion more uniform. 
         [0060]    The second gas diffusion mechanism  11  is fabricated by, for example, bonding with silver solder or indium a first disk in which a number of small holes ha are formed corresponding to gas passages  5   a  of cooling jacket  5  to a second disk in which small holes  11   c  corresponding to gas outlets  6   a  of gas diffusion plate  6  and branching hollow portions ha for making gas that is supplied through gas passages  5   a  flow to small holes  11   c  are formed. The second diffusion mechanism is pressed with uniform force over the whole surface and fixed with e.g., a number of screws onto the cooling jacket. 
         [0061]    With such configuration, a larger coolant channel can be formed. In addition, gas outlets can be formed with high density (preferably more than 1.0/cm2). Therefore, not only can the high cooling efficiency be obtained, but the uniformity of gas flow diffusion can also be maintained. 
         [0062]    Furthermore, only the second disk mentioned above may be used as second gas diffusion mechanism. The second diffusion mechanism can also be fixed with brazing or bonding instead of screws. 
         [0063]    In the embodiment, the second gas diffusion mechanism is prepared separately from the cooling jacket. However, it is also possible to form gas diffusion mechanism in the cooling jacket itself. This example is shown in  FIGS. 7 and 8 . 
         [0064]      FIGS. 7  ( a ) and  7  ( b ) are a cross-sectional view and a view taken along A-A line showing a gas ejection mechanism, respectively. 
         [0065]    Gas branch grooves  31  are formed in the cooling jacket so that gas outlets  6   a   1  formed under coolant channel Sb are communicated with gas passages  5   a  in the example of  FIG. 7 . That is, the configuration that gas outlets are also provided under coolant channel Sb is employed. 
         [0066]    By communicating gas passage  5   a  with a plurality of gas outlets  6   a   1  through branch groove  31 , that is, by forming branch grooves on the cooling jacket surface in contact with the gas diffusion plate so that gas is introduced from one gas passage  5   a  into a plurality of gas outlets  6   a ,  6   a   1 , gas outlets  6   a   1  can be provided just under the coolant channel. Thus, The gas flow uniformity and the cooling efficiency are simultaneously improved. 
         [0067]    When the difference of conductance or gas ejection rate may occur between gas outlets  6   a  under gas passage  5   a  and outlets  6   a   1  communicated with branch groove  31  (i.e., gas outlets under the coolant channel), the outlets under gas passage Sa may be made smaller or removed, whereby the gas flow can be made uniform over the whole gas diffusion plate. 
         [0068]    Here, the width of gas branch groove  31  is preferably about 0.1-2 mm from viewpoints of uniform gas flow formation and cooling efficiency. 
         [0069]    In the example of  FIG. 8 , branch passages  31  of gas passages are formed insides the cooling jacket and connected with gas outlets  6   a   1 . 
         [0070]    With such configuration, the cooling efficiency is further improved as compared with  FIG. 7 . The cooling jacket can be fabricated by, for example, bonding to unite a part where coolant channel Sb and gas passages  5   a  are formed, and parts where gas outlets  6   a ,  6   a   1  and gas branch grooves  31  are formed with brazing such as silver solder, a flexible and low melting-point metal such as indium or a solder. 
         [0071]    In addition, although the heat transfer is reduced, a heat-conductive polymer rubber or a rubber containing fibrous metal may be placed between them or may be used as an adhesive. 
         [0072]    The third embodiment of this invention will be explained using  FIG. 9 . 
         [0073]    In this embodiment, the gas diffusion plate side surface of cooling jacket S is cut to form a disk shaped space as a second gas diffusion mechanism  11 , so that the heat transfer through the process gas is made use of in addition to the heat conduction between the gas diffusion plate and the cooling jacket. 
         [0074]    To achieve this object, the height of the second diffusion mechanism (disk shaped space)  11  is preferably set to 0.1 mm or less, and the internal pressure is preferably adjusted to 100 Pa or higher. Thus, the heat transfer with the process gas between cooling jacket  5  and gas diffusion plate  6  can be greatly increased, which further improves the efficiency to cool the gas diffusion plate. The pressure of about 10 kPa is usually adopted as a upper limit although higher pressure is available so long as the mechanism has enough mechanical strength to stand the pressure. In particular, the pressure of 2-4 kPa is preferably adopted. 
         [0075]    Thus, since the pressure in second diffusion mechanism  11  becomes high compared with that of process chamber  1 , a sealing member  41  such as O-ring is preferably arranged to suppress the gas leak between cooling jacket  5  and gas diffusion plate  6 . In order to measure the pressure in second diffusion mechanism  11 , the above-mentioned space  11  is communicated with a pressure gauge  45  through, e.g., passage  42  which penetrates water cooling jacket  5 , frame member  3 , insulator  46 , process chamber wall  1 ′, and connecting member  44 . There are arranged O-rings  43  between members. However, it is also possible to obtain the pressure in the second diffusion mechanism from the supply gas pressure based on the experimental or calculated relationship between the internal pressure of second diffusion mechanism and the supply gas pressure. 
         [0076]    Although the second diffusion mechanism is made by cutting the surface of cooling jacket as mentioned, it is also made by placing a ring-like disk on the circumference part of cooling jacket surface. Moreover, the space is not restricted to a disk shape and therefore may have the configuration in which the gas diffusion plate is partially in contact with the cooling jacket therein. 
         [0077]    In the embodiments mentioned so far, non-metal material such as Si, Si02, carbon, or the like is preferably used as material of gas diffusion plate  6 . These materials are difficult to be processed and easy to break down. However, in the embodiments as mentioned above, there is no need to form gas distribution grooves in gas diffusion plate  6  itself, and therefore the damage during installation or due to thermal hysteresis during processing can be avoided. The gas diffusion plate may be processed as long as it is possible, though. 
         [0078]    In the case where, e.g., silicon oxide is etched, the gas diffusion plate is preferably made from scavenger material such as Si, which consumes fluorine radicals generated during processing and prevents the reduction of photoresist width. This makes it possible to carry out etching processing of finer patterns. 
         [0079]    Furthermore, there is no special limitation in coolant; for example, water and Fluorinert (trademark) are used. 
         [0080]    In addition, the simultaneous cooling using a coolant and a heat conductive gas such as He is also preferably adopted to cool the substrate in etching processing. 
         [0081]    The gas ejection mechanism of this invention described above can also be applied to various surface processing apparatuses such as a plasma CVD apparatus, an ashing apparatus, a thermal CVD apparatus and the like as well as a etching apparatus. A thermal CVD apparatus is shown in  FIG. 10  as the fourth embodiment of this invention. 
         [0082]      FIG. 10  is a cross-sectional view of a thermal CVD apparatus, in which a heating mechanism is arranged both in a gas ejection mechanism and a substrate holding mechanism. Here, the explanation of the same mechanism as in the first embodiment may be omitted. 
         [0083]    The gas ejection mechanism  2  is composed of a gas diffusion mechanism  4 , a heating mechanism  32  in which a heater  32   b  is incorporated, and a gas diffusion plate  6  being fixed by the clamping mechanism shown in  FIG. 2 . An electrostatic chuck  9  is attached on the top of and a heater  33  such as resistor is incorporated in a substrate holding mechanism  7 . A substrate  40  is heated to a predetermined temperature by supplying an electric current to the heater  33  from a power source  34 . 
         [0084]    The process gas is introduced in the same manner as in the first embodiment and the electric power is supplied to heater  32   b  of heating mechanism  32  from power source  35  for heater. The gas diffusion plate  6  is heated uniformly and efficiently to uniformly eject a process gas that is appropriately decomposed by heat from gas outlets  6   a , which makes it possible to form a uniform film with high quality. 
         [0085]    The shapes and materials of gas diffusion plate, gas passage, first and second gas diffusion mechanisms explained in  FIGS. 1-9  are also applied to a thermal CVD apparatus. However, the material to be selected should be enough heat resistant at the heating temperature. 
         [0086]    The parallel-plate type surface processing apparatuses have been explained so far. In this invention, a gas ejection mechanism may have various shapes such as dome, cylinder, rectangular, a polygonal prism, polygonal pyramid, cone, truncated cone, truncated polygonal pyramid, and round shape. 
         [0087]    As has been mentioned, a gas ejection mechanism of this invention enables it to make gas uniformly flow out of gas outlets of gas diffusion plate and to cool or heat the gas diffusion plate uniformly and efficiently. For this reason, the bending or the crack of gas diffusion plate due to heat can be prevented. Furthermore, in the case of etching processing, etching rate, resist selection ratio, the selection ratio inside the hole, and the etched shape of contact hole can be made uniform over the whole substrate. It is also possible to realize uniform process rate in the cases of thermal CVD, plasma CVD, or ashing processing.