Patent Publication Number: US-2020291514-A1

Title: Film Forming Apparatus and Film Forming Method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-044094, filed on Mar. 11, 2019, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a film forming apparatus and a film forming method. 
     BACKGROUND 
     Patent Document 1 discloses a low-pressure chemical vapor deposition apparatus (LPCVD apparatus) which includes a reaction chamber, a vacuum exhaust device, and a manifold connecting the reaction chamber and the vacuum exhaust device. In the LPCVD apparatus, conductance between the reaction chamber and the manifold is sufficiently higher than the exhaust speed of the vacuum exhaust device. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-257171 
     SUMMARY 
     According to an embodiment of the present disclosure, there is provided a film forming apparatus for forming a predetermined film on a substrate, including: a processing container configured to be capable of being depressurized and into which a film-forming raw material gas generated by vaporizing a liquid raw material or a solid raw material is introduced; a stage provided inside the processing container and configured to place the substrate thereon; and a housing body provided below the processing container and communicating with an exhaust port provided in a bottom portion of the processing container, wherein the housing body includes a housing section configured to house a support member of the stage, and a manifold section provided on a side of the housing section and opened toward the housing section, the manifold section being in communication with an exhaust device, wherein an exhaust space is formed at a side of a lower surface of the stage inside the processing container, and atmosphere above the stage flows into the exhaust space along a peripheral portion of the stage, and wherein a horizontal cross-sectional area of the housing section is smaller than a horizontal cross-sectional area of the exhaust space, and a cross-sectional area of an inlet of the housing section is smaller than a cross-sectional area of an outlet of the housing section. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. 
         FIG. 1  is an explanatory view schematically illustrating the configuration of a film forming apparatus according to an embodiment. 
         FIG. 2  is a perspective view of a housing body in the film forming apparatus of  FIG. 1 . 
         FIG. 3  is an explanatory view schematically illustrating the housing body of  FIG. 2 . 
         FIG. 4  is an explanatory plan view schematically illustrating another example of the housing body. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. 
     In a semiconductor device manufacturing process, various kinds of processes such as a film forming process of forming a predetermined film such as a metal film are repeatedly performed on a semiconductor wafer (hereinafter, referred to as a “wafer”), whereby a desired semiconductor device is manufactured. 
     In the film forming process, a solid raw material or a liquid raw material may be heated and vaporized so as to form a film-forming raw material gas. For example, when forming a ruthenium (Ru) film, Ru 3 (CO) 12 , which is a solid raw material, is heated for sublimation, and a raw material gas thus generated is caused to flow into a processing container of a film forming apparatus by a carrier gas. 
     In this regard, as described above, the technology disclosed in Patent Document 1 discloses a low-pressure chemical vapor deposition apparatus (LPCVD apparatus) including a reaction chamber, an evacuation device, and a manifold that connects the reaction chamber and the evacuation device, in which the conductance between the reaction chamber and the manifold is sufficiently higher than an evacuation speed of the evacuation device. However, as an apparatus configuration for realizing this, there is described only a configuration, in which a manifold and a cylindrical reaction furnace are integrated without separation, and exhaust is performed through a turbo molecular pump and a rotary pump directly installed in the manifold via a gate valve and a conductance valve. 
     The technology disclosed in Patent Document 1 is a batch-type processing apparatus in which a plurality of substrates are placed vertically, and the heating of the substrates is performed by a heater provided outside the reaction furnace. In addition, the apparatus of the technology disclosed in Patent Document 1 does not have a function of vertically moving the substrates up and down, and merely places the substrates on an open-type container having a plurality of slots, generally called a wafer boat. 
     The technology disclosed in Patent Document 1 is not directly applicable to a single-wafer-type film forming apparatus that processes the substrates one by one. In such a single-wafer-type film forming apparatus, uniformity of processing is extremely important. Thus, for example, when a ruthenium (Ru) film is formed on a substrate such as a wafer, it is required that the substrate is placed on a stage having a built-in heater, a raw material gas is supplied from above the substrate, and exhaust is uniformly performed from a peripheral portion of the substrate. In addition, a lifting mechanism needs to be provided at the side of a lower surface of the stage to perform loading/unloading of the substrate. Thus, it is difficult to directly apply the technology disclosed in Patent Document 1 to such an apparatus configuration. In addition, the problem of uniform exhaust still remains. 
     Hereinafter, a film forming apparatus and a film forming method according to the present embodiment will be described with reference to the drawings. In the specification and drawings, elements having substantially the same functional configuration will be denoted by the same reference numeral and redundant description thereof will be omitted. 
       FIG. 1  is an explanatory view schematically illustrating the configuration of a film forming apparatus  1  according to an embodiment, in which a portion of the film forming apparatus  1  is illustrated in a cross section. The film forming apparatus  1  of the present embodiment is configured to form a Ru film on a wafer W as a substrate using Ru 3 (CO) 12 , which is a solid raw material as a film forming material. 
     As illustrated in  FIG. 1 , the film forming apparatus  1  includes a processing container  10  which is capable of being depressurized and configured to accommodate therein a wafer W as a substrate, and a raw material gas supply mechanism  20  configured to supply a film-forming raw material gas to the processing container  10 . 
     The processing container  10  whose interior is formed in a cylindrical shape is made of, for example, a metal material (e.g., an aluminum alloy). A loading/unloading port (not illustrated) through which the wafer W is transferred is formed in a sidewall  11  of the processing container  10 . A gate valve (not illustrated) for opening/closing the loading/unloading port is provided in the loading/unloading port. 
     The raw material gas supply mechanism  20  has a raw material tank for storing the above-mentioned solid raw material. The solid raw material stored in the raw material tank is sublimated to form gas. The gas is supplied from a supply part  22  provided at an upper center of the interior of the processing container  10  into the processing container  10  through a supply pipe  21  together with a carrier gas (e.g., CO). The supply pipe  21  is provided with a valve  23 . In addition, the supply pipe  21  is provided with a heating mechanism (not illustrated) in order to maintain the raw material gas in the supply pipe  21  at a predetermined temperature. 
     A stage  30  on which the wafer W is placed horizontally and which has a circular shape in a plan view is provided inside the processing container  10 . A heater (not illustrated) for heating the wafer W and a chiller flow path (not illustrated) are provided inside the stage  30 . A support member  31  configured to support the stage  30  is provided on the central portion of a lower surface of the stage  30 . The support member  31  passes through an exhaust port  12   a  formed in the center of a bottom wall  12  of the processing container  10 . 
     A lower end of the support member  31  is connected to a lifting mechanism  32 . By driving the lifting mechanism  32  under the control of a controller  100  to be described later, the stage  30  is movable up and down between a first position defined at the upper side and a second position defined at the lower side.  FIG. 1  illustrates the state in which the stage is positioned at the first position. 
     The first position is a processing position at which a film forming process is performed on the wafer W. A processing space S is formed above the stage  30  by the stage  30  located at the processing position and an annular partition wall  13   a  extending from a ceiling wall  13  of the processing container  10  to a peripheral portion of the stage  30 . When the stage  30  is positioned at the processing position, an annular gap K is formed between the peripheral portion of the upper surface of the stage  30  and a lower surface of the partition wall  13   a.  An internal atmosphere of the processing space S is exhausted from the side of the lower surface of the stage  30  through the gap K. 
     The second position is a standby position where the stage  30  waits to deliver the wafer W between a transfer mechanism (not illustrated) of the wafer W entering the processing container  10  through the above-described loading/unloading port (not illustrated) formed in the processing container  10  and lifting pins (not illustrated) provided below the stage  30 . 
     A baffle plate  24  as a gas flow forming member for forming a flow of the raw material gas in the processing space S is provided above the stage  30  in the processing container  10  in a parallel relationship with the stage  30 . The baffle plate  24  is a member that vertically partitions the processing space S, and is supported by a support member (not illustrated). The raw material gas supplied from the aforementioned supply part  22  provided in the center of the ceiling wall  13  moves outwards along an upper surface of the baffle plate  24  and then moves downwards from the outer portion of the baffle plate  24 . Then, the raw material gas flows towards an upper surface of the wafer W on the stage  30 . 
     As illustrated in  FIG. 2 , a housing body  40  is provided in the exhaust port  12   a.  More specifically, the housing body  40  has a housing section  41  configured to house the support member  31  and a manifold section  42  integrated with the housing section  41 . An annular portion  41   a  on an upper surface of the housing section  41  is airtightly connected to a peripheral portion of the exhaust port  12   a  in the bottom wall  12 . 
     An inlet opening portion  42   a  of the manifold section  42  is rectangular in a front view and is opened with respect to the housing section  41 . An outlet opening portion  42   b  of the manifold section  42  has circular shape. An APC valve  43  configured to function as a pressure regulating valve is provided in the outlet opening portion  42   b  of the manifold section  42 . The APC valve  43  has an automatic pressure regulating function and a shutoff function. An opening degree of the APC valve  43  is controlled based on a control signal provided from the controller  100  to be described later, and thus an exhaust flow rate and the like are controlled. The APC valve  43  used in the present embodiment has a diameter of 200 mm and an allowable differential pressure of 7.0 Torr. An exhaust device  44  is connected to the downstream side of the APC valve  43 . As the exhaust device  44 , for example, a turbo molecular pump may be used. In the present embodiment, a turbo molecular pump having a capacity of 1,500 L/s is used. 
     A flange  31   a  is provided on the support member  31  outside a bottom wall  41   c  of the housing section  41 . A bellows  33  is provided between an upper surface of the flange  31   a  and a lower surface of the bottom wall  41   c  of the housing section  41  so as to surround an outer periphery of the support member  31 . The bellows  33  prevents airtightness from being lost at a portion through which the support member  31  penetrates in the bottom wall  41   c  of the housing section  41 . 
     In the film forming apparatus  1  configured as above, a horizontal cross-sectional area of the housing section  41  is set to be smaller than that of the exhaust space E. For example, the horizontal cross-sectional area of the housing section  41  may be 50% or less of that of the exhaust space E, specifically 25% to 35%. In the present embodiment, the exhaust port  12   a  formed in the center of the bottom wall  12  of the processing container  10  and the housing section  41  have the same horizontal cross-sectional area. 
     In the housing body  40  of the film forming apparatus  1 , an inlet cross-sectional area of the housing section  41  is smaller than an outlet cross-sectional area of the housing section  41 , namely a cross-sectional area of the inlet opening portion  42   a  of the manifold section  42 . In other words, the inlet cross-sectional area of the manifold section  42  (the area of the inlet opening portion  42   a ) is set to be larger than the inlet cross-sectional area of the housing section  41 . In addition, a volume B of the manifold section  42  illustrated in  FIG. 3  is equal to or larger than a volume A of the housing section  41 . That is, the volumes have a relationship of B≥A. 
     In addition, in the film forming apparatus  1  according to the present embodiment, as illustrated in  FIG. 3 , an opening end portion  41   d  at the side of the manifold section  42  in the inlet of the housing section  41  and an outlet of the manifold section  42 , namely an opening end portion  42   c,  which is located closest to the hosing section  41  in the outlet opening portion  42   b  at the side of the APC valve  43 , are located on the same straight line in a plan view. 
     As illustrated in  FIG. 3 , an inlet shape of the housing section  41  is a non-true circular shape in a plan view, and has an enlarged opening portion  41   e  at the side of the manifold section  42 . That is, the housing section  41  has a non-true circular inlet shape as a whole in which the enlarged opening portion  41   e  protruding toward the manifold section  42  is formed in an opening of an approximately ¾ circular surrounding the support member  31 . 
     The film forming apparatus  1  configured as described above is provided with the controller  100 . The controller  100  is configured by, for example, a computer including a CPU, memory, and the like, and includes a program storage part (not illustrated). The program storage part also stores a program for controlling the APC valve  43 , the valve  23 , and the like in order to implement wafer processing in the film forming apparatus  1 . The program may be recorded in a non-transitory computer-readable storage medium, and may be installed on the controller  100  from the storage medium. In addition, a portion or all of the program may be implemented by a dedicated hardware (circuit board). 
     Next, a film forming process performed on the wafer W using the film forming apparatus  1  will be described. 
     First, an internal pressure of the processing container  10  is measured in a state in which the valve  23  and the APC valve  43  are in the closed state, and an opening degree of the APC valve  43  is adjusted based on the measurement result, so that the interior of the processing container  10  is set to a predetermined pressure (e.g., 7 Torr to 10 Torr). In this state, the gate valve (not illustrated) provided in the wafer loading/unloading port (not illustrated) of the processing container  10  is opened. The transfer mechanism (not illustrated), which holds the wafer W, enters the processing container  10  from a transfer chamber (not illustrate) having a vacuum atmosphere and located adjacent to the processing container  10  through the loading/unloading port. 
     The wafer W is transferred to above the stage  30  located in the standby position described above. Subsequently, the wafer W is delivered on the lifting pins (not illustrated) staying in a raised state. Then, the transfer mechanism is withdrawn from the processing container  10 , and the gate valve is closed. At the same time, the lifting pins are lowered and the stage  30  is raised so that the wafer W is placed on the stage  30 . Then, the stage  30  moves to the above-described processing position, and the processing space S is formed above the wafer W. 
     Subsequently, the wafer W is heated to a predetermined temperature (e.g., 120 to 300 degrees C., specifically 130 to 250 degrees C.) by the heater (not illustrated) provided inside the stage  30 . When the temperature of the wafer W reaches the predetermined temperature, the opening degree of the APC valve  43  is adjusted so that the internal pressure of the processing container  10  is reduced to a predetermined processing pressure, for example, 0.013 Pa to 133.3 Pa (0.1 mTorr to 1 Torr), specifically 1.3 Pa to 66.5 Pa (10 mTorr to 500 mTorr). 
     After the reduction in internal pressure of the processing container  10  is completed, the opening degrees of the valve  23  and the APC valve  43  are adjusted, and the supply of Ru 3 (CO) 12 , which is a film-forming raw material gas, into the processing space S in the processing container  10  is performed at a predetermined flow rate having a range of, for example, 0.1 sccm to 3.0 sccm, specifically 0.2 sccm to 1.0 sccm. In addition, CO as a carrier gas is caused to flow at a flow rate of 10 sccm to 300 sccm. Thus, the formation of a Ru film on the wafer W is initiated. Then, after the formation of the Ru film is completed, the operations of the valves are performed in an order opposite the above order, and the wafer W is unloaded from the processing container  10 . 
     During the film forming process, the flow of the gas inside the processing container  10  is defined as indicated by arrows in  FIG. 1 . That is, the gas flows downward from the annular gap K between the peripheral portion of the upper surface of the stage  30  and the lower surface of the partition wall  13   a  and is once collected in the exhaust space E. Thereafter, the gas flows from the exhaust port  12   a  having a horizontal cross-sectional area smaller than that of the exhaust space E to the inlet of the housing section  41  of the housing body  40 . 
     In this case, since the exhaust port  12   a  and the inlet of the housing section  41  are located in the center of the exhaust space E, the gas is uniformly exhausted from the peripheral portion of the stage  30  when flowing from the gap K to the exhaust space E. After being once collected in the exhaust space E, the gas is concentrated and exhausted toward the exhaust port  12   a  and the inlet of the housing section  41 . Subsequently, the gas that has flown into the housing section  41  flows into the manifold section  42 . 
     Since the cross-sectional area of the inlet of the manifold section  42  (the area of the inlet opening portion  42   a ) is set to be larger than the cross-sectional area of the inlet of the housing section  41 , the conductance when an internal atmosphere of the housing section  41  flows into the manifold section  42  is large. Therefore, it is possible to perform suitable film forming process by performing appropriate exhaust even under a low pressure. Moreover, in the above embodiment, the volume B of the manifold section  42  is set to be larger than the volume A of the housing section  41 . Accordingly, it is possible to make the internal atmosphere of the housing section  41  flow to the APC valve  43  and the exhaust device  44  in an extremely smooth manner Therefore, it is easy to reduce the internal pressure of the processing space S of the processing container  10  to a pressure lower than that in the related art. 
     Since the inlet of the housing section  41  has a non-true circular shape as a whole in a plan view and the housing section  41  has the enlarged opening portion  41   e  at the side of the manifold section  42 , the conductance of the shape of the inlet of the housing section  41  is increased depending on the shape of the inlet opening portion  42   a  of the manifold section  42 . Of course, the shape of the inlet of the housing section  41  is not limited thereto, and an arbitrary enlarged opening portion  41   e  may be adopted depending on the shape of the inlet opening portion  42   a  of the manifold section  42 . 
     In addition, in the film forming apparatus  1  according to the present embodiment, the opening end portion  41   d  at the side of the manifold section  42  in the inlet of the housing section  41  and the outlet of the manifold section  42 , namely the opening end portion  42   c,  which is located closest to the hosing section  41  in the outlet opening portion  42   b  at the side of the APC valve  43 , are located on the same straight line in a plan view. Accordingly, the conductance when exhausting the gas from the interior of the housing section  41  to the manifold section  42 , the APC valve  43 , and the exhaust device  44  is maximized for the housing body  40  having a configuration in which the APC valve  43  and the exhaust device  44  are not located immediately below the housing section  41 . 
     In such a case, as illustrated in  FIG. 4 , the outlet of the manifold section  42 , namely the opening end portion  42   c  located closest to the housing section  41  in the outlet opening portion  42   b  at the side of the APC valve  43 , may be located closer to the side of the housing section  41  than the opening end portion  41   d  positioned at the side of the manifold section  42  in the inlet of the housing section  41 . That is, as illustrated in  FIG. 4 , the opening end portion  42   c  in the manifold section  42  may be located inward of the inlet of the housing section  41  in a plan view. This makes it possible to further increase the conductance at the time of exhaust, and perform the film forming process at a lower pressure. 
     Then, when the Ru film was formed on the front surface of the wafer W under the above-mentioned conditions, it was possible to improve the deposition rate of Ru compared with the conventional Ru film forming process of about 100 mTorr. The thickness of the Ru film on the front surface of the wafer W was good in uniformity. It is presumed that this is because the gas from the processing space S is first gathered in the exhaust space E, followed by being collectively exhausted toward the exhaust port  12   a,  which is located directly below the exhaust space E and having a horizontal cross-sectional area smaller than that of the exhaust space E, and the inlet of the housing section  41 , followed by causing the gas to flow from the housing section  41  into the manifold section  42  having a larger volume. 
     Moreover, in the present embodiment, it was possible to accurately control the internal pressure of the processing container from 7 Torr 10 Torr, which is used in a preparation stage before the film forming process, to 0.1 mTorr to 1 Torr, which is a pressure used during the film forming process. Moreover, the opening degree of the APC valve  43  was realized at 30%, which is smaller than 50% as the general rated maximum opening degree (opening degree that guarantees control). This was obtained by setting the structure of the housing body  40  according to the embodiment such that the cross-sectional area of the inlet of the manifold section  42  (the area of the inlet opening portion  42   a ) is set to be larger than that of the inlet of the housing section  41  and the volume B of the manifold section  42  is set to be larger than the volume A of the housing section  41 . 
     In addition, the housing body  40  adopted in the above-described embodiment is provided so as to be merely connected to the exhaust port in the bottom portion of the processing container in the film forming apparatus having the lifting mechanism or the like provided below the stage. Thus, it is possible to implement the housing body  40  without largely modifying the existing apparatus. This can be achieved by removing the exhaust pipe connected to the exhaust port in the bottom portion of the processing container of this type of existing film forming apparatus and connecting the housing body  40  to the exhaust port. Thus, the good practicability is provided. 
     In the above description, Ru 3 (CO) 12  is used as the solid raw material for a Ru film, but other solid raw materials may be used. In addition, the present disclosure is applicable to a low-pressure film forming process using a liquid raw material instead of the solid raw material. The solid raw material means a raw material, which is solid at atmospheric pressure and room temperature, and the liquid raw material means a raw material, which is liquid at atmospheric pressure and room temperature. 
     While in the above examples, there has been described the example in which the Ru film is formed, the technology according to the present disclosure is applicable to an apparatus for forming another film using a raw material gas generated by vaporizing a solid raw material or a liquid raw material. 
     While in the above description, the CO gas has been described to be used as a carrier gas, a noble gas such as an Ar gas, or an inert gas such as N 2  may be used as the carrier gas. However, when the CO gas is used, it is possible to prevent the raw material gas from decomposing. 
     It should be noted that the embodiments disclosed herein are exemplary in all respects and are not restrictive. The above-described embodiments may be omitted, replaced or modified in various forms without departing from the scope and spirit of the appended claims. 
     The following configurations also belong to the technical scope of the present disclosure. 
     (1) A film forming apparatus for forming a predetermined film on a substrate, includes: a processing container configured to be capable of being depressurized and into which a film-forming raw material gas generated by vaporizing a liquid raw material or a solid raw material is introduced; a stage provided inside the processing container and configured to place the substrate thereon; and a housing body provided below the processing container and communicating with an exhaust port provided in a bottom portion of the processing container, wherein the housing body includes a housing section configured to house a support member of the stage, and a manifold section provided on a side of the housing section and opened toward the housing section, the manifold section being in communication with an exhaust device, wherein an exhaust space is formed at a side of a lower surface of the stage inside the processing container, and atmosphere above the stage flows into the exhaust space along a peripheral portion of the stage, and wherein a horizontal cross-sectional area of the housing section is smaller than a horizontal cross-sectional area of the exhaust space, and a cross-sectional area of an inlet of the housing section is smaller than a cross-sectional area of an outlet of the housing section. 
     (2) In the film forming apparatus of (1) above, an end portion facing the manifold section in the inlet of the housing section and an end portion facing the housing section in an outlet of the manifold section are located on the same straight line in a plan view, or the end portion facing the housing section in the outlet of the manifold section is located closer to the housing section than the end portion facing the manifold section in the inlet of the housing section. 
     (3) In the film forming apparatus of (1) or (2) above, the horizontal cross-sectional area of the housing section is 50% or less of the horizontal cross-sectional area of the exhaust space in terms of a cross-sectional area ratio. 
     (4) In the film forming apparatus of any one of (1) to (3) above, a volume of the manifold section is equal to or larger than a volume of the housing section. 
     (5) In the film forming apparatus of any one of (1) to (4) above, the inlet of the housing section has a non-true circular shape, and includes an enlarged opening portion defined at a side of the manifold section. 
     (6) In the film forming apparatus of any one of (1) to (5) above, the film-forming raw material gas is a gas obtained by sublimating ruthenium 
     (7) A film forming method of forming a ruthenium film on a surface of a substrate by depositing ruthenium on the surface of the substrate using the film forming apparatus of any one of (1) to (6) above, includes: introducing a raw material gas obtained by sublimating the ruthenium into the processing container; heating the stage to a temperature of 120 degrees C. to 300 degrees C.; and performing a film forming process while maintaining an internal pressure of the processing container at 1.3 Pa to 66.5 Pa. 
     According to the technology of the present disclosure, in a film forming apparatus that forms a predetermined film on a substrate in a processing container using a raw material gas generated by vaporizing a raw material, it is possible to perform suitable film forming process by performing appropriate exhaust even under a low pressure. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.