Substrate processing method and substrate processing device

Abstract

A substrate processing method according to the present disclosure comprises: a processing step in which a substrate is processed by supplying a processing gas into a processing vessel for storing the substrate; a first step in which a halogen-based gas that has passed through a metal pipe is supplied into the processing vessel; and a second step which is performed before the first step and in which a basic gas, which contains nitrogen in a molecule thereof and is used, along with the metal constituting the pipe in the processing step, in order to create a complex compound, is supplied into the processing vessel and adsorbed to a wall surface inside said processing vessel, or adsorbed to a porous body provided to a flow path formed by said pipe or to a partition member, which is provided with a plurality of holes that partition said flow path in the flow path direction and connect the upstream and downstream sides of said flow path to one another.

Description

Substrate processing method and substrate processing apparatus

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus.

[0002] In the manufacture of semiconductor devices, various processes are performed by supplying process gases to substrates, such as semiconductor wafers (hereinafter referred to as wafers), stored in a process chamber via, for example, metal piping. The process gases may contain halogen-based gases that are corrosive to the piping. In such cases, metals constituting the piping may be supplied into the process chamber together with the process gas, potentially contaminating the interior of the process chamber and the substrates. Measures may be taken to prevent such metal contamination.

[0003] In the plasma processing apparatus disclosed in Patent Document 1, BCl is supplied through a gas supply pipe having a stainless steel surface on which a chromium passivation film is formed. ３ In this publication, a halogen-based gas such as fluorine is supplied into a processing vessel, but before supplying the gas into the processing vessel, the gas is filled into the gas supply pipe, thereby generating a reaction product containing chromium. The publication also describes a method of removing the halogen-based gas stored in the gas supply pipe together with the reaction product through a bypass line that bypasses the processing vessel (processing chamber) and exhausts the gas. Patent Document 2 also describes a method of removing HF gas or ClF gas as the halogen-based gas. ３ It is described that when supplying gas to the processing vessel, stainless steel piping having Mn and Cu contents below specific values ​​is used.

[0004] JP 2017-84882 A JP 2020-141039 A

[0005] The present disclosure provides a technique that can suppress metal contamination of a substrate being processed in a processing vessel when a halogen-based gas is supplied into the processing vessel through a metal pipe.

[0006] The substrate processing method of the present disclosure includes a processing step of supplying a processing gas into a processing vessel storing substrates to process the substrates; a first step of supplying a halogen-based gas that has passed through a metal pipe into the processing vessel; and a second step, which is carried out before the first step, of supplying a basic gas containing nitrogen in its molecules into the processing vessel to form a complex compound together with the metal that constitutes the pipe in the processing step, and allowing it to be adsorbed onto a wall surface within the processing vessel, or onto a porous body provided in a flow path formed by the pipe, or onto a partition member that divides the flow path in the flow path direction and has a plurality of holes that connect the upstream side and the downstream side of the flow path.

[0007] The present disclosure can suppress metal contamination of substrates processed in a processing chamber when a halogen-based gas is supplied into the processing chamber through a metal pipe.

[0008] FIG. 1 is a longitudinal side view of an apparatus according to an embodiment of a substrate processing apparatus of the present disclosure. FIG. 2 is a schematic view of the etching apparatus. FIG. 3 is an explanatory view showing an etching method of a comparative example using the etching apparatus. FIG. 4 is an explanatory view showing the etching method of the comparative example. FIG. 5 is an explanatory view showing an etching method of an example using the etching apparatus. FIG. 6 is an explanatory view showing the etching method of the example. FIG. 7 is an explanatory view showing the etching method of the example. FIG. 8 is an explanatory view showing the etching method of the example. FIG. 9 is an explanatory view showing the etching method of the example. FIG. 10 is a schematic view of a complex compound. FIG. 11 is a longitudinal side view of another example of a substrate processing apparatus. FIG. 12 is a longitudinal side view of yet another example of a substrate processing apparatus. FIG. 13 is an explanatory view showing the operation of the substrate processing apparatus. FIG. 14 is an explanatory view showing the operation of the substrate processing apparatus. FIG. 15 is a schematic view of a filter provided in the substrate processing apparatus. FIG. 16 is a schematic view of a filter provided in the substrate processing apparatus. FIG. 17 is a cross-sectional plan view showing piping provided in the substrate processing apparatus. FIG. 18 is an explanatory view showing an image acquired in an evaluation test. FIG. 19 is a graph acquired in an evaluation test.

[0009] [Configuration of Substrate Processing Apparatus] A substrate processing apparatus 1, which is one embodiment of the substrate processing apparatus of the present disclosure, will be described with reference to the vertical side view of Fig. 1. The substrate processing apparatus 1 is an etching apparatus that supplies a processing gas to a film 10 formed on the surface of a wafer W to etch it. The film 10 is, for example, a Si (silicon) film. The processing gas (etching gas) is a halogen-based gas, more specifically, for example, ClF ３ (chlorine trifluoride) gas.

[0010] The substrate processing apparatus 1 includes a processing vessel 11. A transfer port 12 for a wafer W is opened in a sidewall of the processing vessel 11 and is opened and closed by a gate valve 13. A stage 14 for placing the wafer W is provided within the processing vessel 11, and the stage 14 is provided with lift pins (not shown). The wafer W is transferred between the stage 14 and a substrate transfer mechanism that moves in and out of the processing vessel 11 via the lift pins.

[0011] A temperature adjustment unit 15 is embedded in the stage 14, and adjusts the temperature of the wafer W placed on the stage 14. This temperature adjustment unit 15 is configured as a flow path that forms part of a circulation path through which a temperature-adjusting fluid, such as water, flows, and adjusts the temperature of the wafer W by heat exchange with the fluid. However, the temperature adjustment unit 15 is not limited to such a fluid flow path and may be configured as, for example, a heater for resistance heating. Alternatively, the stage 14 may be configured as an electrostatic chuck, and the temperature adjustment unit 15 may be a heater provided in the electrostatic chuck.

[0012] Furthermore, a plurality of exhaust ports 21 are opened, for example, at the bottom of the processing vessel 11, and the upstream end of an exhaust pipe 22 is connected to each exhaust port 21. The downstream end of the exhaust pipe 22 is connected to an exhaust mechanism 24, for example, constituted by a vacuum pump, via a valve 23, which is a pressure change mechanism. By adjusting the opening of the valve 23, the exhaust flow rate in the processing vessel 11 is adjusted, and the pressure in the processing vessel 11 is set to a desired vacuum pressure.

[0013] The ceiling of the processing vessel 11 is configured as a shower head 20. The shower head 20 includes a shower plate 25 facing the stage 14, and gas supplied to a gas diffusion space 26 provided in the shower head 20 is discharged in a shower-like manner from outlets formed in the shower plate 25 toward the stage 14. The processing vessel 11 and the shower head 20 are made of a material different from that of piping 31, which will be described later, and specifically, are made of an aluminum alloy such as A5052 specified in the JIS standard.

[0014] The downstream ends of pipes 31 and 41 are connected to the upper part of the shower head 20, and gas can be introduced from each of the pipes 31 and 41 into the gas diffusion space 26. The upstream side of the pipe 31 is connected to ClF ３ The gas supply mechanism 32 is connected to the ClF ３ The gas supply system includes a reservoir for storing the gas, a valve, and a flow rate adjusting unit such as a mass flow controller for adjusting the flow rate of the gas supplied from the reservoir to the downstream side of the pipe 31. By opening and closing the valve V1, ClF ３ The supply of gas into the processing vessel 11 is switched on and off.

[0015] The pipe 31 is made of metal. More specifically, the pipe 31 is made of ClF ３ In order to prevent corrosion caused by gas, the pipe 31 is made of stainless steel such as SUS316L as specified in the JIS standard, or Hastelloy, and therefore contains chromium (Cr) as an element constituting the pipe 31 in addition to iron or nickel, which are the main components.

[0016] The upstream side of the pipe 41 is connected to NH ３ The gas supply mechanism 42 is connected to a (ammonia) gas supply mechanism 42. The supply mechanism 42 is connected to a ClF ３ Instead of gas, stored NH ３ The configuration is the same as that of the supply mechanism 32 except that the gas is supplied to the downstream side of the pipe 41. By opening and closing the valve V2, the NH ３ The supply of the NH gas into the processing chamber 11 is switched on and off. ３The gas is a gas for suppressing contamination of the inside of the processing vessel 11 and the wafer W by Cr originating from the pipe 31, and its role will be described in detail later.

[0017] The substrate processing apparatus 1 also includes a control unit 100, which is a computer, and the control unit 100 includes a program, a memory, and a CPU. The program contains instructions (steps) for processing the wafer W and transporting the wafer W as described above. The program is stored on a storage medium, such as a compact disc, a hard disk, a magneto-optical disc, or a DVD, and is installed in the control unit 100. The control unit 100 outputs control signals to each component of the substrate processing apparatus 1 based on the program, thereby controlling the operation of each component. Specifically, the operations of the substrate processing apparatus 1 controlled in this manner include, for example, adjusting the temperature of the fluid supplied to the stage 14 (i.e., the processing temperature of the wafer W), opening and closing the valves V1 and V2 and controlling the operation of the supply mechanisms 32 and 42 to supply and cut off the supply of each gas into the processing chamber 11, and adjusting the exhaust flow rate using the valve 23 (i.e., adjusting the pressure inside the processing chamber 11).

[0018] [Processing of Comparative Example] In order to clearly show the effects of the embodiment, processing of wafers W in a comparative example will be described first with reference to the process diagrams of Figures 2 to 4. In this comparative example, wafers W are sequentially transferred to the substrate processing apparatus 1 and processed, and NH ３ Gas is not supplied. In the description, wafers W transferred into the processing vessel 11 and processed may be numbered W1, W2, W3, etc. in order. In addition, in FIGS. 2 to 4 and FIGS. 5 to 9, which are process diagrams of the embodiment described later, the substrate processing apparatus 1 is shown in a simplified form compared to that shown in FIG. 1. In each figure, the etchant ClF ３ The molecule is shown as 51. The Cr compound (described later) is shown as 52.

[0019] The wafer W1 is transferred into the processing chamber 11 and placed on the stage 21. The pressure inside the processing chamber 11 is adjusted to a predetermined level by exhausting the gas from the exhaust port 21, and the temperature of the wafer W1 is also adjusted. ３ As described above, the ClF ３ Although the pipe 31 is made of a metal that is relatively resistant to corrosion by gases, it is difficult to completely prevent corrosion. ３ The gas contains the ClF ３ The gas contains a Cr compound 52, which is a reaction product of the gas and Cr constituting the pipe 31. The Cr compound 52 is, for example, chromium fluoride (CrFx) or CrO ２ F ２ and CrF ３ Cr and ClF in the pipe 31. ３ It is a compound derived from the fluorine in the molecule 51, and is in a gaseous state in the pipe.

[0020] Valve V1 is opened, and ClF is discharged from pipe 31. ３ The gas is supplied into the processing chamber 11 through the shower head 20, and the etching process is started (step S11, FIG. 2). ３ The film 10 on the surface of the wafer W1 is etched by the molecules 51. ３ The Cr compounds 52 also flow toward the processing vessel 11 together with the gas, and at this time, the Cr compounds 52 are adsorbed onto the wall surfaces within the processing vessel 11 and onto the wafer W. The wall surfaces within the processing vessel 11 specifically refer to the surface of the stage 14, which is a structure within the processing vessel 11, and the inner wall surfaces of the processing vessel 11. More specifically, the inner wall surfaces of the processing vessel 11 refer to the side, bottom, and ceiling surfaces within the processing vessel 11 (i.e., the lower surface of the shower plate 25).

[0021] The following additional information is provided regarding the presumed adsorption of the Cr compound 52. The Cr compound 52 is supplied from the piping 31 into the processing vessel 11 via the shower head 20, but the flow path within the shower head 20 is relatively narrow. Due to the influence of changes in the ambient pressure as the Cr compound 52 passes through such a narrow flow path, some of the Cr compound 52 changes from a gaseous state to a solid. Specifically, the Cr compound 52 either changes from a gaseous state to a solid while maintaining the original composition, or changes into a Cr compound 52 with a different composition from the original Cr compound 52 and then turns into a solid. By becoming a solid in this manner, the Cr compound 52 is thought to be adsorbed onto the wafer W or the wall surface within the processing vessel 11 before reaching the exhaust port 21. Because the Cr compound 52 is a solid, it is less likely to flow toward the exhaust port 21 than the Cr compound 52 in a gaseous state. Furthermore, unlike the complexes described below, the Cr compound 52 is less likely to be swept away by the exhaust flow within the processing vessel 11 due to its relatively small molecular size. Therefore, it is considered that the Cr compounds 52 remain adsorbed on the wafer W1 and the wall surface inside the processing chamber 11 .

[0022] After a predetermined time has elapsed since the valve V1 was opened, the valve V1 is closed, and ClF is introduced into the processing vessel 11. ３ The gas supply is stopped, and the etching process of the wafer W is completed (step S12, FIG. 3). Then, the wafer W1 is unloaded from the processing chamber 11. At this time, Cr compounds 52 remain adsorbed on the wafer W1 and the wall surface of the processing chamber 11. In the pipe 31, ClF ３ The stagnation of the gas causes new formation of Cr compounds 52 .

[0023] Thereafter, the wafer W2 is transferred into the processing chamber 11, and the temperature and pressure in the processing chamber 11 are adjusted by placing the wafer W2 on the stage 14 in the same manner as when the wafer W1 was processed. Then, the valve V1 is opened to supply ClF ３ Gas is supplied into the processing chamber 11 via the shower head 20, and the etching process is started. That is, the above-described step S11 is performed again (FIG. 4).

[0024] Similarly to the wafer W1, the wafer W2 was treated with ClF ３The film 10 is etched with the gas. Meanwhile, new Cr compounds 52 are supplied into the processing vessel 11 from the pipe 31, and the newly supplied Cr compounds 52 from the pipe 31 and the Cr compounds 52 desorbed from the wall surface of the processing vessel 11 are adsorbed onto the wafer W2. The Cr compounds 52 supplied from the pipe 31 are adsorbed onto the wall surface of the processing vessel 11, thereby increasing the amount of Cr on the wall surface. Thereafter, the valve V1 is closed, and the etching process of the wafer W is completed. That is, the operation of step S12 described above is performed again. Thereafter, the wafer W2 is unloaded from the processing vessel 11.

[0025] Thereafter, wafers W3, W4, W5, and so on are sequentially transferred into the substrate processing apparatus 1, and steps S11 and S12 are performed for each wafer. That is, a cycle consisting of steps S11 and S12 (referred to as cycle A' for convenience) is repeated, thereby etching each wafer W in turn. As the processing in the apparatus progresses as described above, Cr compounds 52 are supplied into the processing vessel 11 through the piping 31 each time cycle A' is performed. Therefore, as cycle A' is repeated to repeatedly process wafers W, the amount of Cr compounds 52 adsorbed on the wall surface of the processing vessel 11 increases as the number of cycles A' is increased. In other words, Cr contamination within the processing vessel 11 progresses. Therefore, the amount of Cr contamination increases as wafers W are processed later in the processing sequence, and there is a risk that the amount of contamination may exceed the allowable range.

[0026] As mentioned above, ClF ３ Even if the pipe 31 is made of a material that has a relatively high corrosion resistance to the gas, the ClF ３ It is difficult to completely prevent corrosion by gas and prevent the formation of Cr compounds 52. Note that, in order to obtain high corrosion resistance against the flowing gas, a coating technique is known in which a film made of a material such as PTFE is formed on the surface of the pipe, and it is conceivable that this coating could be used to address the problems of the above-mentioned comparative example.

[0027] However, the piping 31 may be formed relatively long so that it is routed over a relatively long distance in a factory building where the substrate processing apparatus 1 is installed. In such a case, the piping 31 is formed by welding a plurality of piping sections together, and it is difficult to apply a coating to the welded section. ２ One possible solution is to supply fluorine gas into the pipe 31 to form a passivation film on the surface of the pipe 31. However, it is difficult to form a passivation film even at a relatively low temperature, and high-temperature treatment is time-consuming. Furthermore, even if these coatings or passivation films are formed, it is difficult to completely prevent corrosion of the pipe 31.

[0028] As described above, Patent Document 1 describes a method in which gas that has accumulated in a pipe and contains substances that contaminate the inside of the processing vessel is discharged by supplying it to a bypass line connected to the pipe, thereby preventing it from being supplied into the processing vessel 11, and then introducing the gas into the processing vessel through the pipe. However, as described above, the pipe 31 of the substrate processing apparatus 1 may be relatively long. The ClF that has accumulated in the pipe 31 is then passed through the bypass line from the pipe 31. ３ If you try to remove the gas, a large amount of ClF ３ This increases the operating costs of the equipment because the gas is wasted, so a solution other than exhausting through such a bypass line is required.

[0029] By the way, ClF ３ It is believed that the Cr compound 52 described above is produced as a result of this exothermic reaction. ２ It is also conceivable to address the problem described in the comparative example by passing a gas through the pipe 31 as a purge gas to remove moisture from the surface of the pipe 31, thereby preventing the formation of Cr compounds 52. However, there is a limit to the amount of moisture that can be removed from the surface of the pipe 31 by this purging. ２The gas itself contains moisture, and therefore, adsorption of moisture onto the surface of the pipe 31 is unavoidable, so other effective countermeasures are required.

[0030] There is a known purifier that adsorbs and removes moisture and metals contained in the gas flowing through the flow path. ３ As for the gas, as mentioned above, it has the property of reacting violently with water, so such a purifier is used for the ClF ３ Since it is difficult to install the filter in the pipe 31 through which the gas flows, a different solution is required.

[0031] [Process of Example] The substrate processing apparatus 1 is configured to perform a process that can address the above-mentioned problems. This process is the process of the example, and the outline of the process is as follows: ３ Before supplying the gas into the processing chamber 11, ３ As will be explained in the evaluation test below, it has been confirmed that the processing of this embodiment suppresses Cr contamination of the wafer W.

[0032] This is presumed to be due to the following mechanism of action: NH ３ The gas molecules are adsorbed on the wall surface inside the processing vessel 11, and ClF ３ When the Cr compound 52 gas is supplied into the processing vessel 11 together with the gas, it reacts with the Cr compound 52. Then, the Cr compound 52 reacts with the metals constituting the pipe 31, such as Cr and NH ３ 5 to 9, which explain the examples, NH ３ The molecule is shown as 53, and the above Cr, NH ３ The metal complex compound composed of a halogen atom and a halogen atom is shown as a Cr complex compound 54. A specific example of the Cr complex compound 54 is (NH ４ ) ３ CrF ６ is.

[0033] The Cr complex compound 54 has a relatively large molecular weight and is therefore considered to be solid in the processing vessel 11. However, since the molecular size of the Cr complex compound 54 is relatively large due to its complex form, it is considered to be more likely to be swept away by the air current in the processing vessel 11 and to flow into the exhaust port 21 than the solid Cr compound 52. Therefore, it is presumed that the evaluation test resulted in the suppression of Cr contamination as described above.

[0034] 5 to 9, the process of the example will be specifically described below, focusing on the differences from the process of the comparative example. First, the process vessel 11 is evacuated to a predetermined pressure, and the valve V2 is opened to introduce NH ３ Gas is supplied, NH ３ The molecules 53 are adsorbed onto the wall surface inside the processing vessel 11 (step S1, FIG. 5). As described above, the wall surface inside the processing vessel 11 includes not only the inner wall surface of the processing vessel 11 but also the surfaces of structures inside the processing vessel 11, such as the surface of the stage 14.

[0035] The valve V2 is closed to allow NH ３ The supply of gas is stopped. Then, the wafer W1 is loaded into the processing chamber 11 and placed on the stage 14. The temperature of the wafer W1 is adjusted, and the inside of the processing chamber 11 is adjusted to a predetermined vacuum pressure. Then, the valve V1 is opened, and ClF ３ The gas is supplied into the processing vessel 11, and ClF ３ The etching process using the molecules 51 is started (step S2, FIG. 6). That is, similar to step S11 of the comparative example, etching of the film 10 on the surface of the wafer W1 is started.

[0036] While etching of the film 10 progresses, ClF ３ The Cr compound 52 supplied into the processing vessel 11 together with the gas and the NH adsorbed on the wall surface in the processing vessel 11 ３The Cr complex compound 54 reacts with the molecule 53 to generate a Cr complex compound 54. The Cr complex compound 54 flows with the exhaust flow in the processing vessel 11 to the exhaust port 21 and is removed from the processing vessel 11. As described above, the removal of Cr from the processing vessel 11 is promoted, and Cr contamination of the wafer W1 is suppressed while the film 10 is etched. Note that the generation of the Cr complex compound 54 reduces the amount of NH ３ The amount of molecule 53 decreases.

[0037] The valve V1 is closed, and ClF is introduced from the pipe 31 into the processing vessel 11. ３ The supply of gas is stopped, and the etching process is completed in the same manner as in step S12 of the comparative example (step S3, FIG. 7). By continuing to exhaust the processing vessel 11, the Cr complex compound 54 is continuously discharged from the processing vessel 11, while the wafer W1 is unloaded from the processing vessel 11.

[0038] Thereafter, the valve V2 is opened with the inside of the processing vessel 11 at a predetermined pressure, and NH ３ The gas is supplied. Therefore, the above-described step S1 is executed again. NH ３ The molecules 53 react with the Cr compounds 52 still adsorbed and remaining on the wall surface of the processing vessel 11 to generate Cr complex compounds 54, which are then removed from the processing vessel 11 by exhaust from the exhaust port 21 (FIG. 8). ３ The molecules 53 are adsorbed onto the wall surface inside the processing vessel 11, and the NH ３ The amount of adsorption of the molecules 53 increases.

[0039] The valve V2 is closed to allow NH ３ The supply of gas is then stopped. After that, the wafer W2 is loaded into the processing chamber 11, and the temperature of the wafer W2 is adjusted by placing it on the stage 14, as in the case of loading the wafer W1, and the temperature inside the processing chamber 11 is adjusted. Then, the valve V1 is opened, and ClF ３ Gas is supplied into the processing chamber 11 to perform etching, and the above-described step S2 is then executed again (FIG. 9).

[0040] As in the etching process for wafer W1, ClF ３ The Cr contained in the Cr compound 52 supplied into the processing vessel 11 together with the gas is absorbed by the NH ３ The molecules 53 form a Cr complex compound 54, which is then removed from the processing vessel 11. ３ The action of the gas removes Cr compounds 52 from inside the processing vessel 11 before step S2 is performed, and the removal of Cr compounds 52 is promoted during the etching process after the start of step S2, so that Cr contamination of wafer W2 is also suppressed while etching of film 10 progresses.

[0041] Thereafter, the valve V1 is closed, and the etching process is completed. That is, step S3 is executed again. After this, wafers W3, W4, W5, ... are successively transferred to the substrate processing apparatus 1, and steps S1 to S3 are executed for each wafer. That is, the cycle consisting of steps S1 to S3 (for convenience, referred to as cycle A) is repeated, and the etching process is performed on each wafer W in turn. For each of wafers W3, W4, W5, ..., NH ３ The gas action causes the wafer W to be loaded into the processing vessel 11 in a state in which removal of Cr compounds 52 that had been adsorbed inside the processing vessel 11 during processing of the wafer W just loaded into the processing vessel 11 has progressed, and the removal of Cr from inside the processing vessel 11 is accelerated during processing. Therefore, Cr contamination of each of the wafers W3, W4, W5, ... is also suppressed.

[0042] As described above, according to the process of the embodiment in which cycle A is repeated, ClF ３ When etching each wafer W using the gas, ClF ３ Before supplying the gas, ３ NH ３ The molecules 53 are adsorbed on the wall surface inside the processing vessel 11. ３The Cr in the Cr compound 52 supplied together with the gas becomes a Cr complex compound 54, which facilitates removal from the processing vessel 11, thereby suppressing Cr contamination in the processing vessel 11 and Cr contamination on the wafer W.

[0043] In the above cycle A, before each wafer W is loaded into the processing vessel 11, NH ３ The gas is supplied into the processing vessel 11, and at that timing, NH ３ The present invention is not limited to supplying NH 3 gas into the processing chamber 11. Specifically, when the wafer W is stored in the processing chamber 11, ３ A gas may be supplied into the processing vessel 11 .

[0044] 8 and 9, even after the wafer W has been subjected to the etching process and is unloaded, there is a risk that the Cr compounds 52 may remain adsorbed on the wall surface of the processing vessel 11. In order to prevent the Cr compounds 52 from being adsorbed on the wafer W to be subsequently transferred into the processing vessel 11 and processed, and to further reduce contamination of the wafer W, the NH ３ The gas supply is preferably performed before the wafer W is transferred into the processing vessel 11. Therefore, when the wafer W is not stored in the processing vessel 11, the NH ３ It is more preferable to supply the gas into the processing vessel 11 .

[0045] In the process of the embodiment in which the above-described cycle A is repeated, NH ３ The gas supply is done, but so NH ３ The gas supply is not limited to being performed every time a wafer W is processed. ３ A cycle of supplying the gas and then etching a plurality of wafers W may be repeated. That is, after step S1 is performed, steps S2 and S3 may be performed multiple times, and then step S1 may be performed again, followed by steps S2 and S3 multiple times. However, in order to reliably suppress Cr contamination of each wafer W, it is preferable to use NH 3 as a pretreatment for each wafer W treatment, as in cycle A.３ A gas supply is preferably provided.

[0046] By the way, the valve V2 is opened to allow NH ３ After supplying the gas, open valve V1 to ３ Even if excessive evacuation is performed (i.e., the pressure in the processing vessel 11 is excessively reduced) before the gas supply is started, the NH ３ The molecule does not completely leave, and NH ３ The effect of suppressing Cr contamination by this has been confirmed.

[0047] The pipe 31 contains Cr as a transition metal, and the treatment in the embodiment has been described as suppressing contamination by this Cr. However, if the pipe 31 contains a transition metal other than Cr, and ClF ３ Even when a compound containing a transition metal other than Cr is supplied into the processing vessel 11 by a gas, the process of the above-described embodiment can be used to form a complex of the transition metal and promote its removal from the processing vessel 11. In other words, this technology can also suppress contamination by transition metal elements other than Cr that belong to groups 3 to 12 of the periodic table. Specifically, contamination by manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), etc. can be suppressed.

[0048] The film 10 to be etched is not limited to a Si film. Depending on the material of the film 10, the halogen-based gas flowing through the pipe 31 may be HF (hydrogen fluoride) gas or F ２ It is only necessary to select an appropriate type of gas, such as HF gas. The halogen-based gas may be a compound gas composed of a halogen element and other elements, such as HF gas, or F ２ The halogen-based gas used is not limited to the above-described fluorine-based gas (gas containing fluorine as a constituent element), and the present technology can also be applied to a gas that does not contain fluorine as a constituent element but contains a halogen element other than fluorine, such as bromine.

[0049] However, ClF ３ When the gas is passed through the pipe 31, the ClF ３ A violent reaction occurs between the gas and the pipe 31, and during this reaction, a relatively large amount of Cr compound 52 is generated due to Cr constituting the pipe 31. Therefore, in this technology, as described above, ClF ３ This is a particularly effective technique for suppressing Cr contamination inside the processing vessel 11 and on the wafer W when passing gas through the processing vessel 11 .

[0050] By the way, NH ３ reacts with Cr to produce the Cr complex compound 54, as shown in FIG. ３ The lone pair of electrons on the nitrogen atom in ３ A coordinate bond is formed between this complex ion and ClF ３ The example shown is an ionic bond with fluorine, a constituent element of the gas (NH ４ ) ３ CrF ６ The Cr complex compound 54 shown below is formed. ３ Similarly, a gas that has basicity (can bond with hydrogen ions) due to the inclusion of nitrogen with a lone electron pair in the molecule is called NH ３ In other words, NH 3 can be used as a gas to form a Cr complex compound and promote the removal of Cr. ３ It's not limited to gas.

[0051] Specific examples of gases that can be used include various amine gases such as trimethylamine, NH ３ By using it instead of a gas, a complex compound of Cr is formed, which can suppress Cr contamination inside the processing vessel 11 and on the wafer W. As described above, it is sufficient that nitrogen has a lone electron pair, so that primary to tertiary amines can be used. ３As mentioned above, the amine gas can form a complex with a transition metal other than Cr. That is, even if the pipe 31 containing a relatively large amount of transition metals other than Cr is used and contamination of the inside of the processing vessel 11 and the wafer W by the transition metals is suppressed, the NH ３ Instead of the gas, an amine gas can be used.

[0052] [Another Configuration Example of the Apparatus] However, the present technology is not limited to application to a substrate processing apparatus that performs etching on a wafer W. Fig. 11 shows a vertical cross-sectional side view of a substrate processing apparatus 1A as another example of a substrate processing apparatus. The substrate processing apparatus 1A forms any film on the wafer W by CVD by supplying a film formation gas to the wafer W. The differences between the substrate processing apparatus 1A and the substrate processing apparatus 1 will be described mainly in terms of the downstream end of a pipe 61 connected to the top of the shower head 20, and the upstream end of the pipe 61 connected to a supply mechanism 62 for a film formation gas via a valve V3. Except for the fact that the film formation gas is stored, the supply mechanism 62 is configured to supply ClF ３ It has the same configuration as the gas supply mechanism 32 .

[0053] In the substrate processing apparatus 1A, the processing chamber 11 is constantly evacuated during operation, just like the substrate processing apparatus 1. In the substrate processing apparatus 1A, a film forming gas is supplied to the wafers W transferred to the substrate processing apparatus 1A to perform film forming processing. During this process, a film is formed not only on the surface of the wafers W but also on the wall surface inside the processing chamber 11. After film formation on a predetermined number of wafers W, NH ３ The gas is supplied into the processing vessel 11 and is adsorbed on the wall surface of the processing vessel 11. ３ The gas is supplied as a cleaning gas into the processing vessel 11, and a cleaning process is performed to remove a film on the wall surface of the processing vessel 11. At this time, the Cr compound 52 is supplied into the processing vessel 11, and as in the etching process in the substrate processing apparatus 1, the Cr compound 52 is absorbed by the adsorbed NH ３ The Cr complex compound 54 reacts with the gas to be formed, thereby facilitating removal from the processing vessel 11. As a result, contamination of the wafer W with Cr that is processed after this cleaning is suppressed.

[0054] As described above, ClF flowing through the pipe 31 ３ The gas is not limited to a processing gas for processing the wafer W. The cleaning process is performed in a state where the wafer W is not stored in the processing vessel 11. In addition, like the substrate processing apparatus 1, the substrate processing apparatus 1A also uses NH ３ When the gas is supplied, the wafer W may or may not be housed in the processing vessel 11 .

[0055] [Another Configuration Example of Etching Apparatus] As described above, NH ３ A method was shown to suppress contamination by transition metals such as Cr by supplying gas to form a complex. ３ The formation of the complex by supplying gas is not limited to being performed inside the processing vessel 11. A configuration in which a porous body (porous body) such as a filter is provided in the gas supply pipe upstream of the shower head 20 and the complex is formed and collected in the filter may also be used. A substrate processing apparatus 1B having such a configuration example will be described with reference to the vertical cross-sectional side view of FIG. 12 , focusing on the differences from the substrate processing apparatus 1.

[0056] The downstream end of pipe 71, in addition to the downstream ends of pipes 31 and 41, is connected to the upper part of the shower head 20 of the substrate processing apparatus 1B, which is an etching apparatus. Gas can be introduced from pipe 71 into the gas diffusion space 26 and supplied into the processing chamber 11. A valve V4 and a filter 70 are provided in this order on the upstream side of pipe 71. Therefore, the filter 70 is provided in the flow path formed by pipe 71. Pipe 71 branches upstream from the position where filter 70 is provided to form pipes 72 and 73. Valves V5 and V6 are provided in pipes 72 and 73, respectively, and the upstream ends of pipes 72 and 73 are connected to pipes 31 and 41, respectively. In this example, ClF is supplied to pipes 71 and 72 in addition to pipe 31. ３ Since gas flows through these pipes 71 and 72, at least these pipes 71 and 72 are made of SUS316L or the like, similar to the pipe 31. ３The pipes 71 and 72 are made of a metal that is resistant to corrosion by gas, and therefore the metal that makes up the pipes 71 and 72 includes Cr.

[0057] Furthermore, in the pipes 31 and 41, a filter 70 is installed upstream of the valves V1 and V2 and downstream of the positions where the pipes 72 and 73 are connected, respectively. Each filter 70 captures foreign matter contained in the gas and prevents the foreign matter from being supplied into the processing vessel 11. Although the filters 70 are not shown in the pipes of the substrate processing apparatus shown so far in FIG. 1 and the like, the filters 70 may also be installed in the pipes. Hereinafter, the filters 70 installed in the pipes 31, 41, and 71, respectively, may be referred to as 70A, 70B, and 70C to distinguish them from one another. ClF ３ The filters 70A and 70C through which gas flows are made of, for example, Al ２ O ３ It is made of ceramics such as aluminum oxide.

[0058] A pressure gauge 74 is provided in the pipe 71 at a position between the filter 70C and the valve V4, and the upstream end of an exhaust pipe (hereinafter referred to as a bypass exhaust pipe) 75 is connected to the pressure gauge 74. The pressure gauge 74 transmits a detection signal corresponding to the pressure in the flow path within the pipe 71 at that position to the control unit 100, and the control unit 100 can detect the pressure in that flow path from the detection signal. A valve V7 is provided in the bypass exhaust pipe 75, and the downstream end of the bypass exhaust pipe 75 is connected to the downstream side of the valve 23 in the exhaust pipe 22. Therefore, the exhaust path formed by the bypass exhaust pipe 75 is connected to the filter 70C via the flow path within the pipe 71.

[0059] Then, by opening the valve V7, the exhaust mechanism 24 can exhaust the pipe 71 and the filter 70C (specifically, the flow path within the filter 70C) via the bypass exhaust pipe 75 without passing through the processing vessel 11. As described above, since the filter 70C is a porous body, the flow path within the filter 70C is formed by holes 79 (not shown in FIG. 12 ) in the porous body.

[0060] Next, the operation of the substrate processing apparatus 1B will be described with reference to Figures 13 to 15, which are schematic diagrams of vertical cross sections of the substrate processing apparatus 1B. Figures 13 to 15 show the open and closed states of valves V1, V2, and V4 to V7, with closed valves indicated by diagonal lines and open valves indicated without diagonal lines. Furthermore, for the pipes supplying gases to the showerhead 20 and the bypass exhaust pipe 75, portions through which gas is flowing are shown thicker than portions through which gas is not flowing. The description will also refer to Figures 16 to 19, which are schematic diagrams showing the vertical cross section of the filter 70C, as appropriate.

[0061] First, with each valve closed, a wafer W is transferred into the processing chamber 11. At this time, for example, a relatively long time has passed since the previous processing of the wafer W, and ClF ３ It is assumed that the gas may contain a relatively large amount of Cr compounds 52 due to the accumulation of gas. Then, as shown in FIG. 13, the valves V6 and V7 are opened, and NH ３ The gas passes through the filter 70C and is exhausted via the bypass exhaust pipe 75. ３ By passing the gas, NH ３ The molecules 53 are adsorbed to the wall surfaces 78 that form the pores 79 of the filter 70C (FIG. 16). The filter 70C is a porous body, so it has a relatively large surface area per unit volume. Therefore, a relatively large amount of NH ３ Molecules 53 are adsorbed and held by filter 70C.

[0062] Next, as shown in FIG. 14, valve V6 is closed, and NH ３ The gas supply is stopped. The filter 70C is exhausted through the bypass exhaust pipe 75, and the adsorbed NH ３ Some of the molecules 53 are detached from the wall surface 78 and removed from the filter 70C (FIG. 17). While the valve V6 is opened and the filter 70C is being evacuated in this manner, the pressure in the pipe 71 detected based on the detection signal output from the pressure gauge 74 is monitored by the control unit 100. When the pressure drops below a preset pressure, the NH ３ The elimination of molecule 53 progresses to NH ３Assuming that the amount of molecules 53 adsorbed on the filter 70C has become appropriate, the valve V7 is closed and the exhaust of the filter 70C is stopped. ３ A portion of the ClF is removed by the filter 70C later. ３ When gas is passed through, NH ３ and ClF ３ This is to prevent excessive heat generation in the filter 70C due to an excessive reaction between the filter 70C and the catalyst 70A.

[0063] Thereafter, as shown in FIG. 15, the valves V4 and V5 are opened, and the ClF 2 remaining in the pipes 31, 71, and 72 is ３ The gas passes through the filter 70C and is supplied toward the wafer W. ３ The Cr compounds 52 contained in the gas are absorbed by the filter 70. ３ The Cr compound 52 reacts with the molecule 53 to produce a solid Cr complex compound 54 (FIG. 18). The Cr complex compound 54, which has a relatively large molecular size, cannot pass through the holes 79 of the filter 70 and is prevented from being supplied into the processing vessel 11. That is, the Cr compound 52 is collected in the filter 70 as the Cr complex compound 54 (FIG. 19). ３ When the film 10 on the surface of the wafer W is etched by the gas, the valves V 4 and V 5 are closed and the wafer W is unloaded from the processing chamber 11 .

[0064] NH ３ and ClF ３ Since these gases react violently with each other, if they are simultaneously flowed toward the filter 70C and merged, there is a risk of fire or an excessively exothermic reaction. ３ Gas and ClF ３ The NH 3 gas is not supplied to the filter 70C at the same time, but is supplied to the filter 70C in sequence. ３ The amount of gas adsorption is adjusted. ３The Cr compounds 52 are captured as Cr complex compounds 54 while the ignition and excessive exothermic reactions when the gas flows through the filter 70C are more reliably suppressed.

[0065] Also, NH ３ When the gas is adsorbed onto the filter 70C, as shown in FIG. ３ The gas is exhausted through the bypass exhaust pipe 75, and does not pass through the processing chamber 11. ３ 14, exhaust is performed using the bypass exhaust pipe 75, so that the exhaust flow does not pass through the processing vessel 11. On the upstream side of the position where the bypass pipe 75 is connected in the pipe 71 where the filter 70C is interposed, NH ３ Before the supply of ClF ３ The gas is in a stagnant state. ３ The gas was previously supplied to the pipe 71 when processing the wafer W transferred to the processing chamber 11. ３ Since the gas remains, Cr compounds 52 may be contained on the upstream side of the pipe 71. However, if NH ３ By adjusting the gas adsorption to the filter and the amount of adsorption, it is possible to prevent the Cr compound 52 from being supplied to the processing vessel 11 and contaminating the inside of the processing vessel 11 .

[0066] In the substrate processing apparatus 1B, the pipes are configured as described above, so that NH 3 can be supplied to the substrate processing apparatus 1B without passing through the filter 70C by opening and closing the valves V1 and V2. ３ Gas, ClF ３ The gases can be supplied into the processing vessel 11. Therefore, steps S1 to S3 described in the description of the substrate processing apparatus 1 are performed, and NH ３ In the processing vessel 11 in which ClF is adsorbed, ３ The wafer W can also be processed by supplying gas.

[0067] For the purpose of explanation, the wafers W that are successively transferred to and processed in the substrate processing apparatus 1B are designated as wafers W1 and W2.３ 13 to 15 may be selectively performed depending on the length of time L1 from when the gas supply is terminated to when the wafer W2 is loaded into the processing vessel 11. Specifically, for example, when the length of time L1 is relatively long and equal to or greater than a predetermined set value, it is assumed that a large amount of Cr compounds 52 is retained in the piping, and the Cr compounds 52 are collected by the filter 70C described with reference to FIGS. 13 to 15 to prevent the Cr compounds 52 from being supplied into the processing vessel 11. When the length of time L1 is shorter than the set value, steps S1 to S3 may be performed to suppress Cr contamination in the processing vessel 11.

[0068] In explaining the effects of the substrate processing apparatus 1B, it has been described that Cr contamination in the processing vessel 11 is suppressed by capturing Cr compounds 52 in the filter 70C, but each transition metal other than Cr exemplified in the description of the substrate processing apparatus 1 is also captured in the same manner as Cr. Therefore, contamination in the processing vessel 11 by metals other than Cr is suppressed in the same manner as contamination in the processing vessel 11 by Cr.

[0069] The filter 70C is detachable from the pipe 71, and can be removed from the pipe 71 as needed for maintenance such as replacement or cleaning. For example, this maintenance may be performed periodically by an operator. A plurality of pipes 71 including this filter 70C, pipes 72 and 73 including valves V5 and V6 attached to the pipe 71, and a bypass exhaust pipe 75 including valve V7 may be provided. Then, while the filter 70C is detached from any of the plurality of pipes 71, the filter 70C and bypass exhaust pipe 75 of the other pipes 71 may be used to perform the operations described with reference to FIGS. 13 to 15 .

[0070] 20 shows a cross-sectional plan view of the pipe 71. In the pipe 71 shown in FIG. 20, instead of a filter 70C being interposed, a mesh 76 is provided to separate the flow path in the pipe 71 into an upstream side and a downstream side. Therefore, the flow path formed by the pipe 71 is provided with the mesh 76 as a partition member that separates the flow path in the flow path direction. The mesh 76 also has a relatively large surface area per unit volume, so that a large amount of NH ３ The molecules 53 can be adsorbed, and the Cr compound 52 can be changed into a Cr complex compound 54 on the surface of the mesh 76 .

[0071] If the mesh 76 has a relatively large mesh size (i.e., the holes formed by the mesh 76), the Cr complex compound 54 is not trapped by the mesh 76 but is supplied into the processing vessel 11. However, even in this case, as described in the first embodiment, the Cr complex compound 54 is easily removed from the processing vessel 11 by being carried by the exhaust gas flow formed in the processing vessel 11, and therefore, Cr contamination is reduced.

[0072] Furthermore, instead of a mesh, a member having a large number of holes, such as a punched plate, may be provided to separate the flow path of the pipe 71. As described above, the flow path of the pipe 71 is not limited to being provided with a porous body, and a partition member having a plurality of holes, such as a mesh or punched plate, may be provided to separate the flow path formed by the pipe 71 into an upstream side and a downstream side and to communicate the upstream side and downstream side of the flow path.

[0073] Although the foregoing description has been given using wafers as an example of the substrate to be processed, substrates processed in the processing chamber 11 include, in addition to wafers, substrates for manufacturing flat panel displays, substrates for manufacturing exposure masks used in photolithography, and dummy substrates processed for the purpose of testing or setting processing parameters in the substrate processing apparatus. Furthermore, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, modified, or combined in various ways without departing from the scope and spirit of the appended claims.

[0074] [Evaluation Tests] Evaluation tests conducted in relation to the present technology will be described. Evaluation Test 1: A pipe made of SUS316L was maintained at 35°C, and ClF was introduced into the pipe. ３ The gas was passed through for 100 hours. ３ After the gas flow was completed, the surface condition of the inner wall of the pipe was observed. ２ No passivation film was formed by passing gas through the substrate.

[0075] Figure 21 is an image of the inner wall of this pipe, and it can be seen that there are areas where the surface condition has been significantly altered. Figure 22 is a graph showing the results of XPS (X-ray photoelectron spectroscopy) performed on this altered area. Note that in Figure 13, the measurement results for some elements, such as Mo, which were detected in trace amounts at each depth, are omitted.

[0076] As shown in the graph of Figure 21, the surface layer of the inner wall has a larger amount of fluorine atoms and oxygen atoms than the deeper part, but the amount of Cr is smaller. ３ It is estimated that a chemical reaction occurred between Cr and ClF. ３ Therefore, as described in the embodiment, the ClF ３ When supplying the gas into the processing vessel 11 by passing it through, it is necessary to take measures to prevent Cr contamination inside the processing vessel 11 .

[0077] As shown in FIG. ３ After the gas flow, significant roughness was observed on the inner wall of the pipe. ３ Instead of gas, F ２ It is believed that the roughness is greater than that caused when other halogen-based gases such as ClF ３ The test results confirmed that when the gas was passed through a pipe made of SUS316L, many Cr compounds flowed downstream of the pipe. ３When the gas is passed through the pipe 31 made of Cr, a relatively large amount of Cr compound 52 is likely to be supplied into the processing vessel 11. ３ Even if such a large amount of Cr compound 52 is supplied by the gas, removal from the processing vessel 11 can be promoted. ３ This is a particularly effective technique when gas is used.

[0078] Evaluation Test 2: In evaluation test 2, substrates B1, B2, and B3 were transported to the substrate processing apparatus 1 in this order and subjected to ClF ３ 2 to 4, and the substrates B2 and B3 were subjected to the processes of steps S1 to S3 of the embodiment described in FIGS. 5 to 9. Therefore, before etching the substrates B2 and B3, NH ３ However, before etching the substrate B1, NH ３ There is no gas supply.

[0079] After the processing, substrates B1 to B3 were removed from the processing vessel 11 and their surfaces were cleaned with a predetermined amount of cleaning liquid. The cleaning liquid was collected and the amount of metal elements contained in the cleaning liquid was measured by inductively coupled plasma mass spectrometry. Therefore, the measured value reflects the environment inside the processing vessel 11. Table 1 below shows the results of evaluation test 1, and the values ​​in the table are the measurement results (unit: atoms / cm 2 ) by a predetermined positive number. Therefore, the larger the value shown in the table, the larger the actual measured amount.

[0080]

[0081] As shown in Table 1, unlike the other elements, the measured amount of Cr was in the order of substrate B1 > substrate B2 > substrate B3, and the measured value decreased each time a substrate was processed. After processing substrate B1, NH ３It is considered that the supply of Cr accelerates the discharge of Cr from the processing vessel 11 due to the generation of the Cr complex compound 54 as described in the embodiment, which resulted in such a result. As described above, the results of Evaluation Test 2 demonstrate the effects of the present technology.

[0082] W: Semiconductor wafer 11: Processing vessel 31: Pipe 51: ClF ３ Molecule 52 NH ３ Molecular 54Cr complex compound

Claims

1. A substrate processing method comprising: a processing step of supplying a processing gas into a processing vessel storing substrates to process the substrates; a first step of supplying a halogen-based gas that has passed through a metal pipe into the processing vessel; and a second step, which is carried out before the first step, of supplying a basic gas containing nitrogen in its molecules into the processing vessel to form a complex compound with the metal that constitutes the pipe in the processing step, and allowing the basic gas to be adsorbed onto the wall surface of the processing vessel, or to a porous body provided in a flow path formed by the pipe, or to a partition member that divides the flow path in the flow path direction and has a plurality of holes that connect the upstream side and downstream side of the flow path.

2. A substrate processing method according to claim 1, wherein the basic gas is ammonia gas or an amine gas.

3. The substrate processing method according to claim 2, wherein the processing gas is the halogen-based gas flowing through the metal pipe, and the processing step is an etching step of etching a film formed on the substrate with the halogen-based gas.

4. A substrate processing method according to claim 3, wherein the halogen-based gas is a fluorine-based gas.

5. A substrate processing method according to claim 4, wherein the halogen-based gas is chlorine trifluoride gas, and the metal constituting the piping contains chromium.

6. A substrate processing method according to any one of claims 1 to 5, wherein the second step is a step of adsorbing the basic gas onto the wall surface inside the processing vessel, and is performed in a state where the substrate is not stored inside the processing vessel.

7. A substrate processing method according to any one of claims 1 to 5, wherein the second step is a step of adsorbing the basic gas into the porous body, and includes a step of supplying the halogen-based gas to the porous body after stopping the supply of the basic gas to the porous body.

8. A substrate processing method according to claim 7, further comprising the step of evacuating the porous body through an exhaust pipe connected to the piping after stopping the supply of the basic gas to the porous body and before carrying out the step of supplying the halogen-based gas to the porous body.

9. A substrate processing apparatus comprising: a processing vessel for storing substrates; a processing gas supply unit for supplying a processing gas into the processing vessel to process the substrates; a metal pipe through which a halogen-based gas flows; a halogen-based gas supply unit for supplying the halogen-based gas into the processing vessel through the pipe; a porous body provided in a flow path formed by the pipe, or a partition member having a plurality of holes that divides the flow path in the flow path direction and connects the upstream side and the downstream side of the flow path; a basic gas supply unit for supplying a basic gas containing nitrogen in its molecules to the porous body or mesh through the flow path for generating a complex compound together with a metal constituting the pipe; and a control unit that outputs control signals to perform a first step of supplying the halogen-based gas into the processing vessel and a second step, which is performed before the first step, of supplying the basic gas to the porous body or the partition member for adsorption.

Images