Patent Publication Number: US-2019181056-A1

Title: Silicon-containing film etching method, computer-readable storage medium, and silicon-containing film etching apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-238355, filed on Dec. 13, 2017, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a method of etching a silicon-containing film formed on a substrate, a non-transitory computer-readable storage medium, and an apparatus of etching the silicon-containing film. 
     BACKGROUND 
     In a semiconductor device, a film containing silicon is applied in a wide variety of applications. For example, a silicon germanium (SiGe) film or a silicon (Si) film is used for a gate electrode, a seed layer or the like. In a manufacturing process of a semiconductor device, the SiGe film or the Si film is formed on a substrate and is etched into a predetermined pattern. 
     Etching of a silicon-containing film such as a SiGe film or a Si film has been conventionally performed by various methods. For example, the SiGe film or the Si film is etched by exposing the SiGe film or the Si film to an etching gas containing F 2 , HF, ClF 3  or HCl. 
     Depending on the state of a silicon-containing film which has been subjected to a previous process before an etching process, it may be necessary to control the in-plane distribution of an etching amount when etching the silicon-containing film. For example, when there is a deviation in the film thickness of the silicon-containing film subjected to the previous process, the in-plane uniformity of etching can be improved by controlling the in-plane distribution of an etching amount, for example, by increasing or decreasing an etching amount at the central portion of the silicon-containing film as compared to an etching amount at the outer peripheral portion thereof. 
     Similarly, even after performing a subsequent process followed by the etching process, it may be necessary to control the in-plane distribution of an etching amount depending on the state of the silicon-containing film. Particularly, along with the miniaturization of semiconductor devices in recent years, the pattern has also been miniaturized. Thus, such control of the etching amount is useful. 
     However, in the etching method of the related art, the state of the silicon-containing film which has been subjected to the previous process before the etching process or the subsequent process after the etching process is not taken into consideration. Therefore, there is room for improvement in the conventional silicon-containing film etching method. 
     SUMMARY 
     Some embodiments of the present disclosure provide a technique of appropriately controlling the in-plane distribution of an etching amount of a silicon-containing film when etching the silicon-containing film formed on a substrate. 
     According to one embodiment of the present disclosure, there is provided a method of etching a silicon-containing film formed on a substrate, including: supplying an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF 3  to the silicon-containing film; and controlling etching amounts at a central portion and an outer peripheral portion of the silicon-containing film by controlling a flow velocity of the etching gas. 
     According to another embodiment of the present disclosure, there is provided a non-transitory computer-readable storage medium storing a program that operates on a computer of a controller for controlling an etching apparatus such that the aforementioned method is performed by the etching apparatus. 
     According to another embodiment of the present disclosure, there is provided an apparatus of etching a silicon-containing film formed on a substrate, including: a chamber in which the substrate is accommodated; a gas supply part configured to supply an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF 3  to the silicon-containing film; an exhaust part configured to discharge the etching gas inside the chamber; and a controller configured to control the gas supply part and the exhaust part, wherein the control part controls etching amounts at a central portion and an outer peripheral portion of the silicon-containing film by controlling a flow velocity of the etching gas. 
    
    
     
       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 a vertical sectional view schematically showing the configuration of an etching apparatus according to an embodiment. 
         FIGS. 2A to 2C  are explanatory views showing the verification results of an in-plane distribution of an etching amount when a flow rate of an etching gas including a ClF 3  gas and an Ar gas is changed. 
         FIGS. 3A to 3C  are explanatory views showing the verification results of an in-plane distribution of an etching amount when a flow rate of an etching gas including an F 2  gas and an Ar gas is changed. 
         FIGS. 4A to 4D  are explanatory views showing the verification results of an in-plane distribution of an etching amount when a flow rate of an etching gas including an F 2  gas is changed. 
         FIGS. 5A to 5C  are explanatory views showing the verification results of an in-plane distribution of an etching amount when an etching gas including an F 2  gas and an Ar gas is used and an internal pressure of a chamber is changed. 
         FIGS. 6A to 6C  are explanatory views showing etching states when an etching gas including an F 2  gas is used. 
         FIG. 7  is a graph showing a difference in incubation time between F 2  and ClF 3 . 
         FIG. 8  is a graph showing a difference in reactivity between F 2  and ClF 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the subject specification and the drawings, elements having substantially the same functional configuration will be denoted by like reference numerals and redundant explanation will be omitted. 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. 
     As a result of intensive investigation conducted by the present inventors, it was found that when etching a silicon-containing film, if an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF 3  is used and if the etching gas is supplied to the silicon-containing film while controlling a flow velocity of the etching gas, it is possible to control etching amounts in the central portion and the outer peripheral portion of the silicon-containing film. That is to say, when a ClF 3  gas was used as the etching gas for the silicon-containing film, it was impossible to control the in-plane distribution of an etching amount of the silicon-containing film. The reason why the in-plane distribution of an etching amount can be controlled by controlling the flow velocity of the etching gas including the fluorine-containing gas will be described in detail in the embodiment described below. 
     &lt;Etching Apparatus&gt; 
     First, the configuration of the etching apparatus according to an embodiment of the present disclosure will be described.  FIG. 1  is a vertical sectional view schematically showing the configuration of an etching apparatus  1  according to the present embodiment. In the present embodiment, a case where a silicon germanium (SiGe) film as a silicon-containing film formed on a wafer W as a substrate is etched in the etching apparatus  1  will be described. In addition, the etching performed in the etching apparatus  1  is a plasma-less gas etching. 
     As shown in  FIG. 1 , the etching apparatus  1  includes a chamber  10  in which the wafer W is accommodated, a mounting table  11  configured to mount the wafer W inside the chamber  10 , a gas supply part  12  configured to supply a processing gas from above the mounting table  11  toward the mounting table  11 , and an exhaust part  13  configured to discharge the processing gas existing in the chamber  10  therethrough. 
     The chamber  10  includes a chamber body  20  and a lid  21 . An upper portion of the chamber body  20  is opened, and the opening is closed by the lid  21 . A top surface of a side wall of the chamber body  20  and a lower surface of the lid  21  are hermetically sealed by a sealing material (not shown), whereby airtightness in the chamber  10  is secured. An airtight etching process space is defined inside the chamber  10 . A loading/unloading port (not shown) for loading and unloading the wafer W therethrough is formed in the side wall of the chamber body  20 . The loading/unloading port can be opened and closed by a gate valve (not shown). 
     The mounting table  11  includes an upper table  30  on which the wafer W is mounted and a lower table  31  fixed to a bottom surface of the chamber body  20  and configured to support the upper table  30 . A temperature controller  32  for adjusting a temperature of the wafer W is provided inside the upper table  30 . The temperature controller  32  adjusts a temperature of the mounting table  11  by circulating a temperature control medium such as, for example, water or the like and controls the temperature of the wafer W mounted on the mounting table  11  to a predetermined temperature. 
     The gas supply part  12  includes a shower head  40  configured to supply the processing gas to the wafer W mounted on the mounting table  11 . The shower head  40  is provided on the lower surface of the lid  21  of the chamber  10  so as face the mounting table  11 . A plurality of supply holes  41  for supplying the processing gas therethrough is formed in a lower surface (shower plate) of the shower head  40 . The shower head  40  may have a diameter at least larger than that of the wafer W in order to uniformly supply the processing gas over the entire surface of the wafer W mounted on the mounting table  11 . 
     In addition, the gas supply part  12  includes an F 2  gas supply source  50  for supplying an F 2  gas, an NH 3  gas supply source  51  for supplying an NH 3  gas, an HF gas supply source  52  for supplying an HF gas, and an Ar gas supply source  53  for supplying an Ar gas. An F 2  gas supply pipe  54  is connected to the F 2  gas supply source  50 , an NH 3  gas supply pipe  55  is connected to the NH 3  gas supply source  51 , an HF gas supply pipe  56  is connected to the HF gas supply source  52 , and an Ar gas supply pipe  57  is connected to the Ar gas supply source  53 . The supply pipes  54  to  57  are connected to a collective pipe  58  which is connected to the above-described shower head  40 . The F 2  gas, the NH 3  gas, the HF gas and the Ar gas are supplied into the chamber  10  from the shower head  40  via the supply pipes  54  to  57  and the collective pipe  58 . 
     Each of the F 2  gas supply pipe  54 , the NH 3  gas supply pipe  55 , the HF gas supply pipe  56  and the Ar gas supply pipe  57  is provided with a flow rate controller  59  for controlling the opening/closing operation of each of the supply pipes  54  to  57  and a flow rate of each of the processing gases. The flow rate controller  59  is constituted by, for example, an opening/closing valve and a mass flow controller. 
     Among the processing gases supplied from the gas supply part  12 , the F 2  gas is an etching gas used for main etching. The NH 3  gas and the HF gas are used for removing a natural oxide film and terminating a film subjected to an etching process. The Ar gas is used as a dilution gas or a purge gas. Instead of the Ar gas, another inert gas such as an N 2  gas or the like may be used, or two or more inert gases may be used. 
     In the gas supply part  12  of the present embodiment, the processing gases are supplied from the shower head  40  to the wafer W. However, the method of supplying the processing gases is not limited thereto. For example, a gas supply nozzle (not shown) may be provided in the central portion of the lid  21  of the chamber  10 , and the processing gases may be supplied from the gas supply nozzle. 
     The exhaust part  13  includes an exhaust pipe  60  installed outside the mounting table  11  and provided at the bottom of the chamber body  20  of the chamber  10 . An exhaust mechanism  61  for evacuating the interior of the chamber  10  is connected to the exhaust pipe  60 . An automatic pressure control valve (APC)  62  is provided in the exhaust pipe  60 . An internal pressure of the chamber  10  is controlled by the exhaust mechanism  61  and the automatic pressure control valve  62 . 
     The etching apparatus  1  is provided with a control part  70 . The control part  70  is, for example, a computer, and includes a program storage part (not shown). In the program storage part, a program for controlling the etching process performed in the etching apparatus  1  is stored. The program may be recorded on a computer-readable storage medium such as a computer-readable hard disk (HD), a flexible disk (FD), a magneto-optical disk (MO), a memory card or the like and may be installed from the storage medium on the control part  70 . 
     &lt;Etching Method&gt; 
     Next, an etching method performed in the etching apparatus  1  configured as above will be described. As described above, in the etching apparatus  1  of the present embodiment, the SiGe film formed on the wafer W is etched. 
     First, in a state in which the gate valve is opened, the wafer W is loaded into the chamber  10  and mounted on the mounting table  11 . The temperature of the mounting table  11  is controlled by the temperature controller  32 , and the temperature of the wafer W mounted on the mounting table  11  is controlled to a predetermined temperature. Further, when the wafer W is mounted on the mounting table  11 , the gate valve is closed to hermetically seal the interior of the chamber  10 , whereby an etching process space is formed in the chamber  10 . 
     Thereafter, the NH 3  gas and the HF gas are supplied into the chamber  10  while regulating the internal pressure of the chamber  10 , whereby the natural oxide film formed on the wafer W is removed. At this time, in addition to the NH 3  gas and the HF gas, the Ar gas may be supplied as a dilution gas. In some embodiments, the NH 3  gas may be first supplied into the chamber  10  to stabilize the internal pressure and then the HF gas may be introduced into the chamber  10 . 
     Thereafter, while supplying the Ar gas as a purge gas into the chamber  10 , evacuation is performed to purge the interior of the chamber  10 . 
     Thereafter, the F 2  gas is supplied as an etching gas into the chamber  10 . At this time, the Ar gas may be added as a dilution gas. Then, the SiGe film on the wafer W is etched by the etching gas. 
     &lt;Etching Control&gt; 
     In the etching apparatus  1 , the SiGe film on the wafer W is etched as described above. Next, a method of controlling the in-plane distribution of an etching amount when etching the SiGe film will be described. 
     As a result of verification under various etching conditions, the present inventors have found that if a flow velocity of the etching gas including the F 2  gas is controlled when etching the SiGe film, it is possible to control etching amounts at the central portion and the outer peripheral portion of the SiGe film. The flow velocity of the etching gas referred to herein is a flow velocity of the etching gas supplied to the SiGe film inside the chamber  10 . The control of the flow velocity of the etching gas is performed by controlling a flow rate of the etching gas supplied to the SiGe film inside the chamber  10  or the internal pressure of the chamber  10 . Based on the verification results, the aforementioned findings will be described below. 
     In general, the F 2  gas or the ClF 3  gas is often used as the etching gas for the SiGe film. In the case of using the F 2  gas or the ClF 3  gas, the present inventors changed the flow rate of the etching gas and compared the in-plane distributions of an etching amount. The flow rate of the etching gas is controlled, for example, by the flow rate controller  59 . In addition, the etching gas contains the Ar gas as a dilution gas. In the present verification, the flow rate of the etching gas as a whole was changed by changing the flow rate of the Ar gas. In the verification using the F 2  gas or the ClF 3  gas, the internal pressure of the chamber  10  is kept constant at 150 to 250 mT. 
     The results of this verification are shown in  FIGS. 2A to 2C and 3A to 3C .  FIGS. 2A to 2C  show the verification results in the case of using the ClF 3  gas, and  FIGS. 3A to 3C  show the verification results in the case of using the F 2  gas. 
     As shown in  FIGS. 2A to 2C , the flow rate of the ClF 3  gas was kept constant at 1 to 50 sccm, but the flow rate of the Ar gas was changed to 150 to 250 sccm, 400 to 600 sccm, and 700 to 1,000 sccm. In such a case, regardless of the flow rate of the etching gas, the etching amount at the central portion was larger than the etching amount at the outer peripheral portion, and there was no change in the tendency of the in-plane distribution of the etching amount. In other words, when the ClF 3  gas is used as the etching gas, it was not possible to control the in-plane distribution of the etching amount. 
     On the other hand, as shown in  FIGS. 3A to 3C , the flow rate of the F 2  gas was kept constant at 50 to 100 sccm, but the flow rate of the Ar gas was changed to 50 to 100 sccm, 200 to 300 sccm, and 300 to 500 sccm. In such a case, as shown in  FIG. 3A , when the flow rate of the etching gas is small, the etching amount at the outer peripheral portion was larger than the etching amount at the central portion. On the other hand, as shown in  FIG. 3C , when the flow rate of the etching gas is relatively high, the etching amount at the central portion was larger than the etching amount at the outer peripheral portion. As shown in  FIG. 3B , when the flow rate of the etching gas is intermediate, it was possible to make the etching amount substantially uniform in the plane. In this way, when the F 2  gas is used as the etching gas, it was possible to control the in-plane distribution of the etching amount by controlling the flow rate of the etching gas. It was also possible to improve the in-plane uniformity of etching. 
     In the verification shown in  FIGS. 3A to 3C , the Ar gas as a dilution gas is mixed with the etching gas. However, even when the F 2  gas alone is used as the etching gas as shown in  FIGS. 4A to 4D , the same tendency was obtained. In the verification shown in  FIGS. 4A to 4D , the flow rate of the F 2  gas was changed to 10 to 50 sccm, 50 to 100 sccm, 100 to 200 sccm, and 200 to 300 sccm. The internal pressure of the chamber  10  was kept constant at 50 to 200 mT. 
     As shown in  FIGS. 4A and 4B , when the flow rate of the etching gas is small, the etching amount at the outer peripheral portion was larger than the etching amount at the central portion. On the other hand, as shown in  FIG. 4D , when the flow rate of the etching gas is relatively high, the etching amount at the central portion was larger than the etching amount at the outer peripheral portion. As shown in  FIG. 4C , when the flow rate of the etching gas is intermediate, it was possible to make the etching amount substantially uniform in the plane. Even when the F 2  gas alone is used as the etching gas in this manner, it was possible to control the in-plane distribution of the etching amount by controlling the flow rate of the F 2  gas. 
     In the verification shown in  FIGS. 3A to 3C , the in-plane distribution of the etching amount was controlled by controlling the flow rate of the etching gas. However, as shown in  FIGS. 5A to 5C , even if the internal pressure of the chamber  10  is controlled, it was possible to control the in-plane distribution of the etching amount. In the verification shown in  FIGS. 5A to 5C , the internal pressure of the chamber  10  is controlled by, for example, the exhaust mechanism  61  of the exhaust part  13  and the automatic pressure control valve  62 . As shown in  FIGS. 5A to 5C , the internal pressure of the chamber  10  was changed to 50 to 100 mT, 150 to 250 mT, and 300 to 500 mT. The flow rate of the F 2  gas as the etching gas was kept constant at 50 to 100 sccm, and the flow rate of the Ar gas was kept constant at 200 to 400 sccm. 
     As shown in  FIG. 5A , when the internal pressure of the chamber  10  is relatively low, the etching amount at the central portion was larger than the etching amount at the outer peripheral portion. On the other hand, as shown in  FIG. 5C , when the internal pressure of the chamber  10  is relatively high, the etching amount at the outer peripheral portion was larger than the etching amount at the central portion. As shown in  FIG. 5B , when the internal pressure of the chamber  10  is intermediate, it was possible to make the etching amount substantially uniform in the plane. As described above, when the F 2  gas is used as the etching gas, it was possible to control the in-plane distribution of the etching amount by controlling the internal pressure of the chamber  10 . 
     As described above, according to the verification results shown in  FIGS. 2A to 5C , if the flow velocity of the etching gas including the F 2  gas (the flow rate of the etching gas or the internal pressure of the chamber  10 ) is controlled when etching the SiGe film, it is possible to control the etching amount at the central portion and the outer peripheral portion of the SiGe film. 
     &lt;Mechanism of Etching Control&gt; 
     Next, a mechanism which controls the etching amounts at the central portion and the outer peripheral portion of the SiGe film by controlling the flow velocity of the etching gas including the F 2  gas in the aforementioned manner will be described.  FIGS. 6A to 6C  are explanatory views showing etching states when the F 2  gas is used as the etching gas. 
       FIG. 6A  shows a case where the flow velocity of the etching gas is relatively low, the flow rate of the etching gas is relatively low, and/or the internal pressure of the chamber  10  is relatively high. In such a case, since the flow velocity of the etching gas is relatively low, there is a tendency for the etching gas to be pulled toward the exhaust part  13 . For this reason, the F 2  gas is easily supplied to the outer peripheral portion of the SiGe film (portions indicated by dotted lines in  FIG. 6A ), but is less likely to be supplied to the central portion. As a result, the etching amount at the outer peripheral portion of the SiGe film is larger than the etching amount at the central portion. 
     On the other hand,  FIG. 6C  shows a case where the flow velocity of the etching gas is relatively high, the flow rate of the etching gas is relatively high, and/or the internal pressure of the chamber  10  is relatively low. In such a case, since the flow velocity of the etching gas is relatively high, there is a tendency that the etching gas is supplied to the SiGe film before being exhausted to the exhaust part  13 . For this reason, the F 2  gas is easily supplied to the central portion (portion indicated by a dotted line in  FIG. 6C ) of the SiGe film, but is less likely to be supplied to the outer peripheral portion. As a result, the etching amount at the central portion of the SiGe film is larger than the etching amount at the outer peripheral portion. 
       FIG. 6B  shows a case where the flow velocity of the etching gas is intermediate. In this case, the etching gas is supplied to the SiGe film substantially uniformly in the plane. As a result, the etching amount of the SiGe film can be made substantially uniform in the central portion and the outer peripheral portion. 
     As described above, the etching amounts at the central portion and the outer peripheral portion of the SiGe film vary depending on whether the flow velocity of the etching gas is high or low. This is because the molecular weight of the F 2  contained in the etching gas is at a low level of 38. That is to say, as will be described later, the F 2  has a small molecular weight, a long incubation time and a moderate reactivity. Therefore, the in-plane distribution of the etching amount varies depending on the flow velocity of the etching gas. 
     On the other hand, when the molecular weight of the F 2  is at a high level of 92.45 as in ClF 3 , the etching gas is likely to be supplied to the central portion of the SiGe film regardless of the flow velocity of the etching gas. Therefore, in the case of using the etching gas including the ClF 3  gas, the etching amount at the central portion becomes larger than the etching amount at the outer peripheral portion. Thus, the in-plane distribution of the etching amount cannot be controlled. 
     Further, as shown in  FIG. 7 , the incubation time of ClF 3  is shorter than that of F 2 . The incubation time is a period of time from the supply of the etching gas to the start of etching.  FIG. 7  is a graph showing a difference in incubation time between F 2  and ClF 3 , in which the horizontal axis indicates the molecular weight and the vertical axis indicates the incubation time. Comparing F 2  and ClF 3 , ClF 3  having a higher molecular weight is shorter in incubation time than F 2  having a lower molecular weight. In addition, this tendency does not depend on a partial pressure. The tendency remains the same regardless of whether the partial pressure is high or low. For this reason, in the case of the etching gas including the ClF 3  gas, ClF 3  reacts immediately with SiGe even if the flow velocity of the etching gas is changed. This makes it difficult to control the in-plane distribution of the etching amount. 
     Further, as shown in  FIG. 8 , ClF 3  is more reactive than F 2 .  FIG. 8  is a graph showing a difference in reactivity between F 2  and ClF 3 , in which the horizontal axis indicates the etching time and the vertical axis indicates the etching amount. Comparing F 2  and ClF 3 , the slope of the graph of ClF 3  is larger than that of F 2 . That is to say, the reaction of ClF 3  is faster than that of F 2 . Therefore, in the case of the etching gas including the ClF 3  gas, ClF 3  is likely to react with SiGe even if the flow velocity of the etching gas is changed. This makes it difficult to control the in-plane distribution of the etching amount. 
     As described above, ClF 3  has a larger molecular weight than F 2 , and the incubation time of ClF 3  is relatively short due to the difference in molecular weight. Moreover, ClF 3  is more reactive than F 2 . Therefore, in the case of the etching gas including the ClF 3  gas, it is difficult to control the in-plane distribution of the etching amount. 
     In other words, F 2  has a smaller molecular weight than ClF 3 , and the incubation time of F 2  is relatively long due to the difference in molecular weight. In addition, the reactivity of F 2  is moderate. Therefore, in the case of using the etching gas including the F 2  gas, as shown in  FIGS. 6A to 6C , it is possible to control the in-plane distribution of the etching amount. 
     Furthermore, as a result of investigation conducted by the present inventors, it was found that if the etching gas contains a fluorine-based gas having a smaller molecular weight than ClF 3 , the incubation time becomes longer and the reactivity becomes moderate. For this reason, it is possible to obtain the same tendency as the tendency shown in  FIGS. 6A to 6C  in the in-plane distribution of the etching amount. Therefore, it is possible to control the in-plane distribution of the etching amount of the SiGe film by controlling the flow velocity of the etching gas containing the fluorine-based gas having a smaller molecular weight than ClF 3 . 
     &lt;Application Example of Etching Control&gt; 
     Next, application examples of the above etching control will be described. As the application examples, description will be made on a case where the etching control is applied to the setting of etching conditions (application example 1), a case where the etching control is applied to a feed-forward control based on the state of the silicon-containing film subjected to a previous process before etching (application example 2), a case where the etching control is applied to a feed-back control based on the state of the silicon-containing film subjected to a subsequent process followed by etching (application example 3), and a case where the etching control is applied to a feed-back control based on the state of the silicon-containing film immediately after etching (application example 4). 
     Application Example 1 
     The etching condition setting of the application example 1 will be described. In the application example 1, first, an etching gas including an F 2  gas is supplied to a wafer Wc for etching condition setting to etch an SiGe film. The wafer Wc is not a product wafer W manufactured on an in-line basis but is a wafer used only for setting the etching conditions. Thereafter, the in-plane distribution of the etching amount of the etched SiGe film is measured. Any well-known method may be used for measuring the etching amount. Thereafter, based on the measurement result, the etching amount of the SiGe film is set in the plane so that the SiGe film after the etching has a desired size in the plane. The flow velocity of the etching gas is set based on this etching amount. For example, when it is desired to make an etching amount at the central portion of the SiGe film larger than an etching amount at the outer peripheral portion, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively high. Under the conditions thus set, the product wafer W is etched. 
     Application Example 2 
     The feed-forward control of the application example 2 will be described. In the application example 2, the previous process before etching is performed on a wafer W manufactured on an in-line basis. Thereafter, immediately before the wafer W is loaded into the etching apparatus  1 , the state of the SiGe film formed on the wafer W, for example, the film thickness of the SiGe film is measured. Any well-known method can be used for the measurement of the film thickness. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when the measurement result indicates that the film thickness at the central portion of the SiGe film is larger than the film thickness at the outer peripheral portion, the etching amount at the center portion is set larger than the etching amount at the outer peripheral portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when the measurement result indicates that the film thickness at the outer peripheral portion of the SiGe film is smaller than the film thickness at the central portion, the etching amount at the outer peripheral portion is set larger than the etching amount at the central portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively low. Then, the wafer W is etched under the corrected set conditions. 
     Application Example 3 
     The feed-back control of the application example 3 will be described. In the application example 3, the subsequent process followed by etching is performed on a wafer W manufactured on an in-line basis, the state of the SiGe film formed on the wafer W, for example, the film thickness of the SiGe film is measured. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when the measurement result indicates that the film thickness at the central portion of the SiGe film is larger than the film thickness at the outer peripheral portion, the etching amount at the central portion is set larger than the etching amount at the outer peripheral portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when the measurement result indicates that the film thickness at the outer peripheral portion of the SiGe film is smaller than the film thickness at the central portion, the etching amount at the outer peripheral portion is set larger than the etching amount at the central portion in the etching process. In such a case, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively low. Then, a subsequent wafer W is etched under the corrected set conditions. 
     Application Example 4 
     The feed-back control of the application example 4 will be described. In the application example 4, immediately after etching, the state of the SiGe film formed on the wafer W manufactured on an in-line basis, for example, the film thickness of the SiGe film is measured. Thereafter, the flow velocity of the etching gas is corrected based on the measurement result. For example, when it is desired to make the etching amount at the central portion of the SiGe film larger than the etching amount at the outer peripheral portion, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively high. On the other hand, for example, when it is desired to make the etching amount at the outer peripheral portion of the SiGe film larger than the etching amount at the central portion, the flow rate of the etching gas and the internal pressure of the chamber  10  are set so that the flow velocity of the etching gas becomes relatively low. Then, a subsequent wafer W is etched under the corrected set conditions. 
     Other Embodiment 
     In the above embodiment, the etching control when etching the SiGe film has been described. However, the etching control of the present disclosure may also be applied to other silicon-containing films. 
     For example, when etching a silicon (Si) film, for example, a mixed gas of an F 2  gas and an NH 3  gas is used as the etching gas. The gas to be mixed with the F 2  gas is not limited to the NH 3  gas and may be any basic gas. 
     As in the above embodiment, it is possible to control the in-plane distribution of the etching amount of the Si film by controlling the flow velocity of the etching gas including the F 2  gas and the NH 3  gas. That is to say, by increasing the flow velocity of the etching gas, the etching amount at the central portion of the Si film can be made larger than the etching amount at the outer peripheral portion. Further, by lowering the flow velocity of the etching gas, the etching amount at the outer peripheral portion of the Si film can be made larger than the etching amount at the central portion. Since the mechanism of etching control of the Si film is similar to the mechanism of etching control of the SiGe film of the above embodiment, the detailed description thereof will be omitted. 
     According to the present disclosure in some embodiments, it is possible to appropriately control an in-plane distribution of an etching amount of a silicon-containing film by controlling a flow velocity of an etching gas including a fluorine-containing gas having a smaller molecular weight than ClF 3  when etching the silicon-containing film formed on a substrate. 
     Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to this embodiment. Those having ordinary knowledge in the technical field to which the present disclosure belongs may clearly appreciate that various modifications or changes can be conceived within the scope of the technical idea described in the claims. It is understood that these modifications or changes fall within the technical scope of the present disclosure as well.