Etching method and etching apparatus

Abstract

The etching method includes a process (a), a process (b), a process (c), and a process (d). In the process (a), a substrate having a base layer and an etching target film formed on the base layer is provided on a stage. In the process (b), a plasma is generated from a processing gas. In the process (c), the etching target film is etched by supplying a bias power having a first frequency to the stage to form a recess. In the process (d), the etching target film is further etched by changing the frequency of the bias power to a second frequency different from the first frequency in accordance with the aspect ratio of the recess after the process (c). In the etching method, the etching target film is continuously etched from after the plasma is generated to until the base layer is exposed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an etching method and an etching apparatus. BACKGROUND

[0002] Various methods for forming a high-aspect-ratio pattern with high precision have been proposed. For example, there is a method in which a high-frequency (RF: Radio Frequency) bias power for attracting ions is supplied to a stage on which a substrate is placed to promote etching in the depth direction.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2008-192906 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present disclosure provides a technology for improving shape abnormalities of a pattern formed on a substrate by etching.

[0008] SOLUTION TO PROBLEM

[0009] An etching method of one embodiment of the present disclosure includes the following steps: step (a) in which a substrate having a base layer and an etching target film formed over the base layer is provided to a stage; step (b) in which a plasma is generated from a processing gas; step (c) in which the etching target film is etched by supplying a bias power having a first frequency to the stage to form a recess; and step (d) in which the etching target film is further etched by changing the frequency of the bias power to a second frequency different from the first frequency in accordance with the aspect ratio of the recess after the step (c), in the etching method, the etching target film is continuously etched from after the plasma is generated to when the base layer is exposed.

[0010] EFFECT OF THE INVENTION

[0011] According to the present disclosure, the effect of being able to improve shape abnormalities of a pattern formed on a substrate by etching is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 FIG. 1 is an example of a flowchart showing a flow of an etching method according to a first embodiment.

[0013] Figure 2A FIG. 2 is an example of a view showing a substrate to which the etching method according to the first embodiment is applied.

[0014] Figure 2B is a view showing a pattern formed on a substrate.Figure 2A A diagram showing an example of a recessed portion of a substrate.

[0015] Figure 3 This is a diagram illustrating an example of the relationship between the frequency of the RF bias power and the opening size (CD: Critical Dimension) of the formed recess 400.

[0016] Figure 4 This is used to illustrate further steps while maintaining the RF bias power frequency at a first frequency. Figure 2B The diagram shows the etching process of the substrate.

[0017] Figure 5 This is used to explain how changing the frequency of the RF bias power from a first frequency to a second frequency further affects... Figure 2B The diagram shows the etching process of the substrate.

[0018] Figure 6 This is a diagram illustrating an example of when the RF bias power is changed.

[0019] Figure 7 This is a flowchart illustrating an example of the process of the etching method according to the second embodiment.

[0020] Figure 8 It shows that it was formed in Figure 2A Another example of the recessed portion of the substrate is shown in the figure.

[0021] Figure 9 This is used to illustrate further steps while maintaining the RF bias power frequency at a first frequency. Figure 8 The diagram shows the etching process of the substrate.

[0022] Figure 10 This is used to explain how changing the frequency of the RF bias power from a first frequency to a second frequency further affects... Figure 8 The diagram shows the etching process of the substrate.

[0023] Figure 11 This is used to explain how changing the frequency of the RF bias power from the second frequency to the third frequency further affects... Figure 10 The diagram shows the etching process of the substrate.

[0024] Figure 12 This is a diagram showing the outline structure of the etching apparatus involved in the embodiment. Detailed Implementation

[0025] Embodiments of the etching method and the etching apparatus disclosed in the present application will be described below in detail with reference to the accompanying drawings. In addition, each of the embodiments can be appropriately combined within a range not causing the processing contents to contradict each other. Furthermore, the same reference numerals are assigned to the same or equivalent portions in each of the drawings.

[0026] Hereinafter, in the description of each of the embodiments, a direction substantially perpendicular to the surface of the substrate will be referred to as a thickness direction or a depth direction when the direction of a pattern formed on the substrate is described. In addition, a direction substantially parallel to the surface of the substrate will be referred to as a horizontal direction. In the case where the substrate is substantially disc-shaped, a direction parallel to the surface of the substrate from the center of the disc toward the circumference will be referred to as a radial direction.

[0027] In the following description, a "pattern" refers to the entirety of shapes formed on a substrate. The pattern refers to, for example, the entirety of a plurality of shapes such as holes, trenches, lines, and line-and-spaces formed on a substrate. In addition, a "recess" refers to a portion of a shape in a pattern formed on a substrate that is recessed in the thickness direction of the substrate. In addition, the recess has a "side wall" that is an inner circumferential surface of the recessed shape, a "bottom" that is a bottom portion of the recessed shape, and a "top" that is a substrate surface in the vicinity of the side wall and is continuous with the side wall. In addition, a space surrounded by a corner of the top of the recess will be referred to as an "opening". Furthermore, the term "opening" is also used to refer to the entirety of a space or an arbitrary position of a space surrounded by the bottom and the side wall of the recess. In addition, a horizontal direction dimension in the space formed by the recess will be referred to as an "opening dimension". In addition, a ratio of the depth of the recess (a dimension from the top of the recess to the bottom) to the opening dimension of the top (opening end) of the recess will be defined as an "aspect ratio".

[0028] It is known that shape abnormalities occur when etching is performed in order to form a pattern with a high aspect ratio. For example, a phenomenon called bowing in which the inner circumferential surface of a hole expands in the horizontal direction is known when a hole is formed in the depth direction. In addition, a phenomenon called tapering in which a hole gradually becomes smaller toward the bottom of the hole is known. In order to improve this shape abnormality, it is desirable to provide not only a technique for promoting etching in the depth direction but also a technique capable of controlling the shape of a recess formed by etching during etching.

[0029] (One example of a flow of the etching method according to the first embodiment)

[0030] Figure 1 is a flowchart illustrating one example of a flow of the etching method according to the first embodiment. The etching method according to the first embodiment controls the shape of a recess formed on a substrate during execution of etching by changing the frequency of RF bias power supplied to a substrate table on which the substrate is placed during execution of etching.

[0031] First, a substrate is provided (step S101). For example, a substrate having a base layer, an etching target film formed on the base layer, and a mask formed on the etching target film is provided. The substrate is carried into a processing chamber in which a stage is provided inside, and is placed on the stage.

[0032] Next, a plasma is generated from a processing gas in the processing chamber (step S102). Next, the stage on which the substrate is placed is supplied with RF bias power having a first frequency to etch the etching target film (step S103). In step S103, ions in the plasma are attracted to the etching target film to etch the etching target film. By the etching of the etching target film, a pattern including a recess is formed on the substrate.

[0033] Next, depending on the aspect ratio of the recess formed by the etching, the frequency of the RF bias power is changed to a second frequency different from the first frequency to further etch the etching target film (step S104).

[0034] After that, it is determined whether the pattern formed, for example, the recess satisfies a prescribed condition (step S105). In the case where it is determined that the prescribed condition is not satisfied (step S105: "No"), the process returns to step S104 and is continued. On the other hand, in the case where it is determined that the prescribed condition is satisfied (step S105: "Yes"), the process is ended.

[0035] Further, the determination in step S105 is performed, for example, based on whether the cumulative processing time of the etching of step S104 reaches a prescribed time.

[0036] <Example of pattern formed in first embodiment>

[0037] Figure 2A is a drawing illustrating an example of a substrate to which the etching method according to the first embodiment is applied. Figure 2A The substrate 300 illustrated has a base layer 301, an etching target film 302, and a mask 303. In the etching method according to the first embodiment, first, the substrate 300 is placed on a stage in step S101. Next, a plasma is generated from a processing gas in step S102. Next, in step S103, the stage is supplied with RF bias power having a first frequency to etch the etching target film 302. As the first frequency, for example, a frequency of 0.1 MHz or more and 1 MHz or less, or 0.1 MHz or more and less than 1 MHz is used. Here, let the first frequency be 400 kHz.

[0038] As Figure 2BAs shown, by the etching of step S103, the etching target film 302 and the mask 303 on the base layer 301 form a recess 400. The recess 400 has a bottom 400B, a side wall 400S, and a top 400T. In Figure 2B the state, the bottom surface of the recess 400 (the surface of the bottom 400B) is located inside the etching target film 302. Figure 2B is a view showing the recess 400 formed in the state of Figure 2A the substrate S shown in the view.

[0039] In Figure 2B , the opening size (width) of the recess 400 gradually decreases from the top 400T toward the bottom 400B. It is considered that the change in the opening size of the recess 400 is caused by the magnitude (400 kHz) of the frequency of the RF bias power supplied to the stage. The inventors of the present application changed the frequency of the RF bias power to investigate the change in the opening size of the recess 400 formed.

[0040] Figure 3 is a view showing an example of the relationship between the frequency of the RF bias power and the opening size of the recess 400 formed. Figure 3 is a view in which the CD of the recess 400 formed by etching the substrate 300 while changing the frequency of the RF bias power supplied to the stage is plotted in association with the depth of the recess 400. The etching is performed until the recess 400 penetrates the etching target film 302 and the bottom surface of the recess 400 (the surface of the bottom 400B) reaches the base layer 301, that is, until the base layer 301 is exposed. As shown in Figure 3 , in the case where the frequency of the RF bias power is 13 MHz, the CD of the recess 400 increases near the center in the depth direction, and the recess 400 becomes an arcuate shape. In contrast, in the case where the frequency of the RF bias power is 400 kHz, the CD of the recess 400 gradually decreases as the depth increases, and the recess 400 becomes a tapered shape. As such, according to the results of Figure 3 , it is found that the shape of the recess 400 changes depending on the frequency of the RF bias power supplied to the stage. That is, it is found that the smaller the frequency of the RF bias power, the more the depth position at which the CD is the largest moves upward, and the closer the recess 400 becomes to a tapered shape. On the other hand, it is found that the larger the frequency of the RF bias power, the more the depth position at which the CD is the largest moves downward, and the closer the recess 400 becomes to an arcuate shape.

[0041] Here, it is assumed that the state of maintaining Figure 2B (the state in which the frequency of the RF bias power supplied to the stage is maintained at the first frequency (400 kHz)) is maintained to progress the etching and the bottom 400B of the recess 400 reaches the base layer 301. Then, the opening size of the recess 400 decreases as the depth increases. In this case, as shown inFigure 4 As shown, the recess 400 becomes a cone shape. Figure 4 This is used to illustrate further steps while maintaining the RF bias power frequency at a first frequency. Figure 2B The diagram shows the etching process of the substrate 300.

[0042] In contrast, Figure 1 In the etching method according to the first embodiment shown, the shape of the recess 400 formed on the substrate 300 is controlled by changing the frequency of the RF bias power supplied to the stage. That is, in the etching method according to the first embodiment, the frequency of the RF bias power is changed to a second frequency different from the first frequency according to the aspect ratio of the recess 400, to further etch the target film 302. Figure 1 (Step S104).

[0043] The change of the RF bias power frequency in step S104 is performed as follows. First, referring to data (hereinafter referred to as "shape data") representing the shape of the recess 400 formed when the etch target film 302 is etched to the substrate layer 301 at each frequency of the RF bias power, the shape of the recess 400 corresponding to the first frequency is determined. The shape data is expressed, for example, by formulas or tables. Figure 3This data shows the relationship between the frequency of the RF bias power and the opening size (CD) of the formed recess 400. The shape data is predetermined through experiments, simulations, etc. The shape data is stored, for example, in a storage unit of the etching apparatus. Furthermore, when the shape of the recess 400 corresponding to the first frequency is determined by referring to the shape data, a second frequency is selected based on the determined shape of the recess 400. For example, if the determined shape of the recess 400 is a conical shape, a frequency higher than the first frequency is selected as the second frequency. Alternatively, for example, if the determined shape of the recess 400 is an arc shape, a frequency lower than the first frequency is selected as the second frequency. Here, referring to the shape data, the shape of the recess 400 corresponding to the first frequency (400kHz) is determined to be a conical shape, and a frequency higher than the first frequency is selected as the second frequency. As the second frequency, any frequency higher than the first frequency (400kHz) is acceptable; for example, it can be selected from frequencies between 1MHz and 13MHz. Here, the second frequency is assumed to be 13MHz. Furthermore, based on the shape of the recess 400 determined by the shape data, the aspect ratio at the depth position where the opening size (width) of the recess 400 reaches the lower limit of a predetermined allowable range is calculated (hereinafter appropriately referred to as "aspect ratio at the depth position"). Moreover, at the time point when the aspect ratio of the recess 400 after etching in step S103 reaches the calculated aspect ratio at the depth position, the frequency of the RF bias power is changed to the selected second frequency (13MHz). In other words, at the time point when the aspect ratio of the recess 400 after etching in step S103 reaches the calculated aspect ratio at the depth position (an example of any time point within the predetermined allowable range where the opening size of the recess 400 is), the process in step S103 ends, and the process in step S104 is executed. The aspect ratio of the recess 400 is estimated, for example, using the elapsed time since the start of step S103 or the state of the plasma. The state of the plasma refers to, for example, luminescence intensity. In order to suppress the abnormal shape of the opening of the recess 400, such as a conical shape, which narrows from top to bottom, the position at which the opening size is at its maximum depth can be moved downward by increasing the frequency of the RF bias power as the aspect ratio of the recess 400 increases.

[0044] Figure 5 This is used to explain how changing the frequency of the RF bias power from a first frequency to a second frequency further affects... Figure 2B The diagram shows the etching process of the substrate 300. This is achieved by changing the frequency of the RF bias power while... Figure 2B Etching the substrate 300 allows the depth position of the opening size to be moved downwards. Thus, as... Figure 5As shown, it is possible to expand the size (width) of the bottom 400B of the recess 400 and form the side wall 400S of the recess 400 substantially vertically. As a result, the shape of the recess 400 can be changed from Figure 2B the shape shown in Figure 5 to the rectangular shape shown in

[0045] In addition, in the first embodiment, during the period from the generation of plasma in step S102 until the base layer 301 is exposed, the etching target film 302 can be continuously etched. Also, during this period, plasma can be continuously generated from the processing gas, and bias power can be continuously supplied to the stage. As described above, in the first embodiment, by performing etching while changing the frequency of the RF bias power, shape abnormalities such as bowing can be suppressed. Therefore, there is no need to form a protective film on the side wall 400S of the recess 400 during the middle of etching, and processing can be performed with high productivity.

[0046] <Timing of change of RF bias power>

[0047] Figure 6 is a diagram for explaining an example of the timing of change of the RF bias power. In Figure 6 , the relationship between the frequency of the RF bias power and the opening size (CD) of the formed recess 400 is shown (see Figure 3 ). Here, let the first frequency be 400 kHz and the second frequency be 13 MHz. Also, it is preferable that the CD of the recess 400 is included within the allowable range of 140 nm to 150 nm.

[0048] As Figure 6 shown, when etching progresses by supplying bias power having the first frequency (400 kHz) to the stage ( Figure 1 , step S103), as the depth increases, the opening size (CD) of the recess 400 gradually decreases. And when the depth reaches about -2.0 μm, the CD of the recess 400 reaches 140 nm which is the lower limit value of the allowable range. In this case, the aspect ratio at a depth of about -2.0 μm is the above-mentioned "aspect ratio at the depth position". And when the aspect ratio of the recess 400 formed by the etching in step S103 reaches the above-mentioned "aspect ratio at the depth position" (the aspect ratio at a depth of about -2.0 μm), the frequency of the RF bias power is changed to the second frequency (13 MHz). Thereby, at a depth position exceeding the above-mentioned "aspect ratio at the depth position", the impact of ions on the side wall 400S of the recess 400 can be promoted, and the depth position where the CD is maximum can be further moved downward. That is, by expanding the size (width) of the bottom 400B of the recess 400 at a depth position exceeding the above-mentioned "aspect ratio at the depth position", finally the shape of the recess 400 can be made close to a rectangular shape.

[0049] (Effect of the first embodiment)

[0050] The etching method according to the first embodiment includes the process (a), the process (b), the process (c), and the process (d). In the process (a), a substrate having a base layer and an etching target film formed on the base layer is provided on a stage. In the process (b), a plasma is generated from a processing gas. In the process (c), the etching target film is etched by supplying a bias power having a first frequency to the stage to form a recess. In the process (d), the etching target film is further etched by changing the frequency of the bias power (for example, RF bias power) to a second frequency different from the first frequency in accordance with the aspect ratio of the recess after the process (c). In the etching method according to the first embodiment, the etching target film is continuously etched from the time when the plasma is generated until the base layer is exposed. Therefore, according to the first embodiment, by changing the frequency of the RF bias power as the aspect ratio of the recess formed by etching increases, it is possible to control the shape of the recess formed. Therefore, according to the first embodiment, it is possible to improve the shape abnormality of a pattern formed on the substrate by etching.

[0051] In addition, in the first embodiment, it can be that, in the process (d), the shape of the recess corresponding to the first frequency is determined with reference to data indicating the shape of the recess formed by etching the etching target film to reach the base layer for each frequency of the bias power. Also, it can be that, in the process (d), the second frequency is selected based on the determined shape of the recess. Therefore, according to the first embodiment, by selecting the frequency of the bias power to be adjusted in accordance with the shape of the recess formed by etching, it is possible to control the shape of the recess. Therefore, according to the first embodiment, it is possible to further improve the shape abnormality of a pattern formed on the substrate by etching.

[0052] In addition, in the first embodiment, it can be that, in the process (d), in a case where the determined shape of the recess is a tapered shape, a frequency larger than the first frequency is selected as the second frequency. Also, it can be that, in the process (d), in a case where the determined shape of the recess is an arcuate shape, a frequency smaller than the first frequency is selected as the second frequency. Also, according to the first embodiment, in a case where the shape abnormality of a pattern occurs due to etching, it is possible to select the frequency of the bias power to control the shape of the recess so that the shape of the recess becomes a shape that eliminates the shape abnormality. Therefore, according to the first embodiment, it is possible to further improve the shape abnormality of a pattern formed on the substrate by etching.

[0053] Further, in the first embodiment, it can also be that, based on the determined shape of the recess, the process (c) is ended and the process (d) is started before the opening size of the recess corresponding to the first frequency becomes an upper limit value of a predetermined allowable range (at the time point of becoming the upper limit value or before becoming the upper limit value). Alternatively, it can also be that, based on the determined shape of the recess, the process (c) is ended and the process (d) is performed before the opening size of the recess corresponding to the first frequency becomes a lower limit value of a predetermined allowable range (at the time point of becoming the lower limit value or before becoming the lower limit value). Thus, according to the first embodiment, the frequency of the bias voltage power can be adjusted to control the shape of the recess so as to avoid the opening size of the recess formed by etching from deviating from the allowable range. Thus, according to the first embodiment, the shape abnormality of the pattern formed on the substrate by etching can be further improved.

[0054] Further, in the first embodiment, it can also be that, based on the determined shape of the recess, the range of the aspect ratio of the depth position at which the opening size of the recess corresponding to the first frequency reaches the upper limit value or the lower limit value of the predetermined allowable range is determined. Also, it can be that the process (c) is ended and the process (d) is performed within the determined range of the aspect ratio of the recess. Thus, according to the first embodiment, the frequency of the bias voltage power can be adjusted to control the shape of the recess so as to avoid the opening size of the recess formed by etching from deviating from the allowable range. Thus, according to the first embodiment, the shape abnormality of the pattern formed on the substrate by etching can be further improved.

[0055] Further, in the first embodiment, it can also be that the aspect ratio of the recess after the process (c) is estimated using the elapsed time from the start of the process (c) or the state of the plasma. Thus, in the first embodiment, it can also be that the frequency is changed from the first frequency to the second frequency according to the elapsed time from the start of the process (c) or the emission state of the plasma described above.

[0056] Further, in the first embodiment, it can also be that the recess having an aspect ratio of 50 or more is finally formed in the etching target film. Thus, according to the first embodiment, in the case where a pattern having a high aspect ratio is formed on the substrate by etching, the shape abnormality of the formed pattern can also be improved.

[0057] (Second Embodiment)

[0058] The above first embodiment controls the shape of the formed recess by changing the frequency of the RF bias voltage power supplied to the stage once. Not limited thereto, the frequency of the RF bias voltage power can also be changed multiple times. As a second embodiment, an example in which the frequency of the RF bias voltage power is changed to a plurality of frequencies different from each other in stages is described.

[0059] Figure 7 This is a flowchart illustrating an example of the etching method according to the second embodiment. First, a substrate is provided (step S201). For example, a substrate having a base layer, an etch target film formed on the base layer, and a mask formed on the etch target film is provided. The substrate is moved into a processing chamber internally equipped with a mounting stage and placed on the mounting stage.

[0060] Next, plasma is generated from the process gas in the processing chamber (step S202). Then, an RF bias power with a first frequency is supplied to the stage on which the substrate is placed to etch the target film (step S203). In step S203, ions in the plasma are attracted to the target film to etch it. By etching the target film, a pattern including recesses is formed on the substrate.

[0061] Next, based on the aspect ratio of the recess formed by etching, the frequency of the RF bias power is changed to a second frequency different from the first frequency to further etch the etched film (step S204).

[0062] Next, based on the aspect ratio of the recess formed by etching, the frequency of the RF bias power is changed to a third frequency different from the second frequency to further etch the etched film (step S205).

[0063] Next, it is determined whether the formed pattern, such as the recess, meets the specified conditions (step S206). If it is determined that the specified conditions are not met (step S206: "No"), the process returns to step S205 to continue processing. On the other hand, if it is determined that the specified conditions are met (step S206: "Yes"), the process ends.

[0064] <An example of a pattern formed in the second embodiment>

[0065] The substrate 300 to which the etching method of the second embodiment is applied and Figure 2A The substrate 300 shown is the same. In the etching method according to the second embodiment, firstly, in step S201, the substrate 300 is placed on a mounting stage. Next, in step S202, plasma is generated from a process gas. Next, in step S203, RF bias power having a first frequency is supplied to the mounting stage to etch the target film 302. As the first frequency, for example, a frequency of 1MHz to 13MHz is used. Here, the first frequency is assumed to be 13MHz.

[0066] like Figure 8As shown, through etching in step S203, an etched target film 302 and a mask 303 are formed on the substrate layer 301 to create a recess 400. The recess 400 has a bottom 400B, sidewalls 400S, and a top 400T. Figure 8 In this state, the bottom surface of the recess 400 (the surface of the bottom 400B) is located within the etched object film 302. Figure 8 It shows that it was formed in Figure 2A A diagram showing another example of the recess in the substrate S.

[0067] exist Figure 8 In the recess 400, the opening size (width) increases near the bottom 400B. This change in opening size is believed to be caused by the magnitude (13MHz) of the frequency (first frequency) of the RF bias power supplied to the stage. That is, according to... Figure 3 As the results show, the higher the frequency of the RF bias power, the further down the opening size (CD) moves to the depth position where the maximum depth is located, and the closer the recess 400 is to an arc shape.

[0068] Here, it is set to maintain. Figure 8 The state (i.e., maintaining the frequency of the RF bias power supplied to the stage at a first frequency (13MHz)) causes etching to proceed, and the bottom 400B of the recess 400 reaches the substrate layer 301. Thus, as the depth increases and horizontal etching progresses, the inner peripheral surface of the recess 400 (the surface surrounded by the sidewalls 400S) expands horizontally. In this case, as... Figure 9 As shown, the recess 400 becomes an arc shape. Figure 9 This is used to illustrate further steps while maintaining the RF bias power frequency at a first frequency. Figure 8 The diagram shows the etching process of the substrate 300.

[0069] In contrast, Figure 7 In the etching method according to the second embodiment shown, the shape of the recess 400 formed on the substrate 300 is controlled by changing the frequency of the RF bias power supplied to the stage. That is, in the etching method according to the second embodiment, the frequency of the RF bias power is changed to a second frequency different from the first frequency according to the aspect ratio of the recess 400, to further etch the target film 302. Figure 7 (Step S204).

[0070] The change of the RF bias power frequency in step S204 is performed as follows: First, referring to the shape data mentioned above, the shape of the recess 400 corresponding to the first frequency is determined. The shape data is expressed, for example, by formulas or tables. Figure 3The data shown is the relationship between the frequency of the RF bias power and the opening size (CD) of the recess 400 formed. Also, when the shape of the recess 400 corresponding to the first frequency is determined with reference to the shape data, the second frequency is selected based on the determined shape of the recess 400. For example, in the case where the determined shape of the recess 400 is a tapered shape, a frequency larger than the first frequency is selected as the second frequency. Also, for example, in the case where the determined shape of the recess 400 is an arcuate shape, a frequency smaller than the first frequency is selected as the second frequency. Here, with reference to the shape data, the shape of the recess 400 corresponding to the first frequency (13 MHz) is determined to be an arcuate shape, and a frequency smaller than the first frequency is selected as the second frequency. As the second frequency, a frequency smaller than the first frequency (13 MHz) is selected, for example, from a frequency of 0.1 MHz or more and 1 MHz or less, or a frequency of 0.1 MHz or more and less than 1 MHz. Here, the second frequency is set to 400 kHz. Also, a depth position at which the depth-to-width ratio of the recess 400 at which the opening size (width) of the recess 400 reaches the upper limit value of the predetermined allowable range is calculated based on the determined shape of the recess 400. Also, at the point in time at which the depth-to-width ratio of the recess 400 after the etching of step S203 reaches the calculated depth position depth-to-width ratio, the frequency of the RF bias power is changed to the selected second frequency (400 kHz). In other words, at the point in time at which the depth-to-width ratio of the recess 400 after the etching of step S203 reaches the calculated depth position depth-to-width ratio (an example of an arbitrary point in time at which the opening size of the recess 400 is within the predetermined allowable range), the processing of step S203 ends, and the processing of step S204 is executed. In the case where a shape abnormality in which the inner circumferential surface of the recess 400 expands in the horizontal direction, like an arcuate shape, is to be suppressed, the progress of etching in the horizontal direction can be delayed by decreasing the frequency of the RF bias power as the depth-to-width ratio of the recess 400 increases.

[0071] Figure 10 is a diagram for explaining a case where the substrate 300 is etched further by changing the frequency of the RF bias power from the first frequency to the second frequency. Figure 8 The data shown is the relationship between the frequency of the RF bias power and the opening size (CD) of the recess 400 formed. Also, when the shape of the recess 400 corresponding to the first frequency is determined with reference to the shape data, the second frequency is selected based on the determined shape of the recess 400. For example, in the case where the determined shape of the recess 400 is a tapered shape, a frequency larger than the first frequency is selected as the second frequency. Also, for example, in the case where the determined shape of the recess 400 is an arcuate shape, a frequency smaller than the first frequency is selected as the second frequency. Here, with reference to the shape data, the shape of the recess 400 corresponding to the first frequency (13 MHz) is determined to be an arcuate shape, and a frequency smaller than the first frequency is selected as the second frequency. As the second frequency, a frequency smaller than the first frequency (13 MHz) is selected, for example, from a frequency of 0.1 MHz or more and 1 MHz or less, or a frequency of 0.1 MHz or more and less than 1 MHz. Here, the second frequency is set to 400 kHz. Also, a depth position at which the depth-to-width ratio of the recess 400 at which the opening size (width) of the recess 400 reaches the upper limit value of the predetermined allowable range is calculated based on the determined shape of the recess 400. Also, at the point in time at which the depth-to-width ratio of the recess 400 after the etching of step S203 reaches the calculated depth position depth-to-width ratio, the frequency of the RF bias power is changed to the selected second frequency (400 kHz). In other words, at the point in time at which the depth-to-width ratio of the recess 400 after the etching of step S203 reaches the calculated depth position depth-to-width ratio (an example of an arbitrary point in time at which the opening size of the recess 400 is within the predetermined allowable range), the processing of step S203 ends, and the processing of step S204 is executed. In the case where a shape abnormality in which the inner circumferential surface of the recess 400 expands in the horizontal direction, like an arcuate shape, is to be suppressed, the progress of etching in the horizontal direction can be delayed by decreasing the frequency of the RF bias power as the depth-to-width ratio of the recess 400 increases. Figure 8 Figure 9 Figure 10 ​​​

[0072] However, in Figure 10 In this state, the recess 400 becomes a tapered shape that gradually tapers from the middle of the depth direction to the front end. When in Figure 10 In this state, it is difficult to form the sidewalls 400S perpendicularly during further etching. Therefore, it is sometimes difficult to form a pattern perpendicular in the depth direction.

[0073] Therefore, in Figure 7 In the etching method according to the second embodiment shown, the shape of the recess 400 formed on the substrate 300 is further controlled by further changing the frequency of the RF bias power supplied to the stage. That is, based on the aspect ratio of the recess 400, the frequency of the RF bias power is changed to a third frequency different from the second frequency used immediately before the change, in order to further etch the film 302 to be etched. Figure 7 (Step S205). The third frequency can also be appropriately selected based on the shape of the recess 400 corresponding to the second frequency. Here, the shape of the recess 400 corresponding to the second frequency (400kHz) is tapered, therefore, a frequency larger than the second frequency is selected as the third frequency. The third frequency can be selected, for example, from a frequency of 5MHz or higher and 40MHz or lower. In the case of suppressing the abnormal shape of the recess 400, such as the tapered shape, where the opening narrows from top to bottom, horizontal etching can be promoted at deeper locations by increasing the frequency of the RF bias power as the aspect ratio of the recess 400 increases. That is, more etching can be performed on the sidewall 400S near the bottom 400B of the recess 400.

[0074] Figure 11 This is used to explain how changing the frequency of the RF bias power from the second frequency to the third frequency further affects... Figure 10 The diagram shows the etching process of the substrate 300. This is achieved by changing the frequency of the RF bias power to a third frequency while etching... Figure 10 The substrate 300 is etched, which promotes horizontal etching at deeper locations. Thus, as... Figure 11 As shown, the size (width) of the bottom 400B of the recess 400 can be increased and the sidewalls 400S of the recess 400 can be formed substantially vertically. As a result, the shape of the recess 400 can be changed from... Figure 10 The shape shown becomes Figure 11 The rectangular shape shown.

[0075] Further, in the second embodiment, the etching of the etching target film 302 can be continuously performed during a period from the generation of the plasma in step S202 to the exposure of the base layer 301. In this period, the plasma can be continuously generated from the processing gas, and the bias power can be continuously supplied to the stage. As in the first embodiment, in the second embodiment, too, it is not necessary to perform a process of forming a protective film on the side wall 400S of the recess 400 or the like in the middle of the etching, and the processing can be performed at a high productivity.

[0076] (Effects of the second embodiment)

[0077] In the method according to the second embodiment, after the process (d), at least one of the following processes can be performed once or more: the etching target film is further etched by changing the frequency of the bias power to a frequency different from the frequency immediately before the change, according to the aspect ratio of the recess. Thus, according to the second embodiment, by changing the frequency of the RF bias power to a plurality of frequencies different from each other as the aspect ratio of the recess formed by the etching increases, the shape of the recess formed can be controlled. For example, the frequency of the RF bias power can be made smaller to ensure the etching rate at a stage where the aspect ratio of the recess formed is small, and the frequency of the RF bias power can be made larger to promote the etching in the horizontal direction at a deep position as the aspect ratio of the recess increases. Thus, according to the second embodiment, the shape abnormality of the pattern formed can be suppressed.

[0078] (Structure example of the etching apparatus according to the embodiments)

[0079] Figure 12 is a diagram showing a schematic structure of an etching apparatus 10 according to the embodiments. Figure 12 The etching apparatus 10 shown can be used to implement the etching method according to the embodiments. Figure 12 The etching apparatus 10 shown is a so-called inductively-coupled plasma (ICP) apparatus having a plasma source for generating an inductively-coupled plasma. However, the etching apparatus according to the embodiments can utilize a plasma generated by another method. For example, the etching apparatus according to the embodiments can be an apparatus utilizing a capacitively-coupled plasma (CCP), an electron-cyclotron-resonance plasma, a helicon-wave-excited plasma (HWP), or a surface-wave plasma (SWP), or the like.

[0080] The etching apparatus 10 includes a processing chamber 12. The processing chamber 12 is formed of a metal such as aluminum. The processing chamber 12 is, for example, a substantially cylindrical shape. A space 12c in which processing is performed is provided in the processing chamber 12.

[0081] A substrate support table (also referred to as a stage) 14 is disposed below the space 12c. The substrate support table 14 is configured to hold a substrate W placed thereon. The substrate W is, for example, a substrate processed by the etching method of one embodiment.

[0082] The substrate support table 14 can be supported by a support mechanism 13. The support mechanism 13 extends upward from the bottom of the processing chamber 12 within the space 12c. The support mechanism 13 can be substantially cylindrical. The support mechanism 13 can be formed of an insulating material such as quartz.

[0083] The substrate support table 14 includes an electrostatic chuck 16 and a lower electrode 18. The lower electrode 18 includes a first plate 18a and a second plate 18b. The first plate 18a and the second plate 18b are formed of a metal such as aluminum. The first plate 18a and the second plate 18b are, for example, substantially cylindrical. The second plate 18b is disposed on the first plate 18a. The second plate 18b is electrically connected to the first plate 18a.

[0084] The electrostatic chuck 16 is disposed on the second plate 18b. The electrostatic chuck 16 includes an insulating layer and a thin film electrode disposed in the insulating layer. The thin film electrode of the electrostatic chuck 16 is electrically connected to a direct-current power supply 22 via a switch 23. The electrostatic chuck 16 generates an electrostatic force in accordance with a direct-current voltage of the direct-current power supply 22. The electrostatic chuck 16 adsorptively holds the substrate W by the generated electrostatic force.

[0085] An edge ring FR is disposed on the second plate 18b and around the second plate 18b in a manner so as to surround the outer periphery of the substrate W and the electrostatic chuck 16 when the etching apparatus 10 is in operation. The edge ring FR has a function of improving the uniformity of a process. The edge ring FR is formed of, for example, silicon.

[0086] A flow path 24 is formed in the second plate 18b. A heat exchange medium such as a refrigerant for temperature control is supplied to the flow path 24 from a temperature adjustment unit (e.g., a cooling unit) disposed outside the processing chamber 12. The temperature adjustment unit adjusts the temperature of the heat exchange medium. The heat exchange medium is supplied to the flow path 24 from the temperature adjustment unit through a pipe 26a. The heat exchange medium supplied to the flow path 24 from the temperature adjustment unit is returned to the temperature adjustment unit through a pipe 26b. The heat exchange medium is returned to the flow path 24 in the substrate support table 14 after the temperature adjustment by the temperature adjustment unit. In this manner, the temperature of the substrate support table 14, i.e., the temperature of the substrate W, can be adjusted.

[0087] The etching apparatus 10 is also provided with a gas supply line 28 that passes through the substrate support table 14 and extends to the upper surface of the electrostatic chuck 16. A heat exchange gas such as helium (He) gas is supplied from the heat exchange gas supply mechanism through the gas supply line 28 to the space between the upper surface of the electrostatic chuck 16 and the lower surface of the substrate W. In this way, heat exchange between the substrate support table 14 and the substrate W is promoted.

[0088] In addition, a heater HT can also be provided in the substrate support table 14. The heater HT is a heating device. The heater HT is, for example, embedded in the second plate 18b or the electrostatic chuck 16. The heater HT is connected to a heater power source HP. By supplying electric power to the heater HT from the heater power source HP, the temperature of the substrate support table 14, and further the temperature of the substrate W, can be adjusted.

[0089] The lower electrode 18 of the substrate support table 14 is connected to a high frequency (RF, radio frequency) power source 30 via a matcher 32. The RF power source 30 generates RF bias power, and supplies the RF bias power to the lower electrode 18 to attract ions to the substrate W placed on the substrate support table 14. The RF power source 30 can change the frequency of the RF bias power in a range of, for example, from 400 kHz to 40.68 MHz. The RF power source 30 is an example of a bias power source. In addition, the RF power source 30 can include a plurality of RF power sources that differ in the frequency of the generated RF bias power. In this case, it can be configured so that the frequency of the RF bias power supplied to the lower electrode 18 can be changed by a switching switch provided on the downstream side of the plurality of RF power sources.

[0090] In addition, instead of the RF power source 30, a voltage pulse power source configured to supply a voltage pulse other than RF power can be used. Here, the voltage pulse refers to a pulse-shaped voltage in which the magnitude of the voltage periodically changes. The voltage pulse power source is configured to be able to change the frequency of the voltage pulse. The voltage pulse power source can be a direct current power source. The voltage pulse power source can be configured so that the voltage pulse is supplied from the power source itself, or can be configured so that a device that makes the voltage pulse is provided on the downstream side. In one example, the voltage pulse is supplied to the lower electrode 18 in a manner so as to generate a negative potential on the substrate W. The voltage pulse can be a rectangular wave, a triangular wave, can be an impulse, or can have another waveform. It can be that the voltage pulse power source is able to change the frequency (pulse frequency) of the voltage pulse in a range of, for example, 100 kHz to 2 MHz. In addition, the voltage pulse power source can include a plurality of voltage pulse power sources that differ in the frequency of the generated voltage pulse. In this case, as with the RF power source described above, it can be configured so that the frequency of the voltage pulse supplied to the lower electrode 18 can be changed by a switching switch provided on the downstream side of the plurality of voltage pulse power sources.

[0091] Further, instead of supplying the RF bias power or voltage pulse to the lower electrode 18, the bias electrode provided in the electrostatic chuck 16 can be supplied with the RF bias power or voltage pulse.

[0092] The etching apparatus 10 is further provided with a shield 34 which is detachably attached to the inner wall of the processing chamber 12. The shield 34 is configured to surround the outer periphery of the support mechanism 13. The shield 34 prevents the byproducts generated by the processing from adhering to the processing chamber 12. The shield 34 can also be an aluminum member coated with a ceramic such as Y2O3.

[0093] An exhaust path is formed between the substrate support table 14 and the side wall of the processing chamber 12. The exhaust path is connected to an exhaust port 12e formed in the bottom of the processing chamber 12. The exhaust port 12e is connected to an exhaust device 38 via a pipe 36. The exhaust device 38 includes a pressure adjusting portion and a vacuum pump such as a turbo molecular pump (TMP). A partition 40 is disposed in the exhaust path, i.e., between the substrate support table 14 and the side wall of the processing chamber 12. The partition 40 has a plurality of through holes which pass through the partition 40 in the thickness direction. The partition 40 can also be an aluminum member coated with a ceramic such as Y2O3.

[0094] An opening is formed in the upper side of the processing chamber 12. The opening is closed by a window 42. The window 42 is formed of a dielectric such as quartz. The window 42 is, for example, a flat plate.

[0095] A suction port 12i is formed in the side wall of the processing chamber 12. The suction port 12i is connected to a gas supply portion 44 via a pipe 46. The gas supply portion 44 supplies various gases used in the processing to the space 12c. The gas supply portion 44 is provided with a plurality of gas sources 44a, a plurality of flow controllers 44b, and a plurality of valves 44c. The gas supply portion 44 is connected to the suction port 12i via the pipe 46. The gas supply portion 44 is connected to the suction port 12i via the pipe 46. Figure 12 Although not shown in the figure, a plurality of suction ports different for each of the supplied gases can be provided to avoid mixing of the gases.

[0096] The plurality of gas sources 44a include gas sources of various gases described later. One gas source can supply one or more kinds of gases. The plurality of flow controllers 44b can be mass flow controllers (MFCs), and the flow controllers 44b achieve flow control by pressure control. Each of the gas sources included in the plurality of gas sources 44a is connected to the suction port 12i via a corresponding one of the plurality of flow controllers 44b and a corresponding one of the plurality of valves 44c. The position of the suction port 12i is not particularly limited. For example, the suction port 12i can be formed in the window 42 instead of being formed in the side wall of the processing chamber 12.

[0097] An opening 12p is formed in a side wall of the processing chamber 12. The opening 12p is a carrying-in and carrying-out path of the substrate W which is carried into and carried out from the space 12c of the processing chamber 12 from the outside. A gate valve 48 is provided on the side wall of the processing chamber 12, and the gate valve 48 can open and occlude the opening 12p.

[0098] An antenna 50 and a shield 60 covering the antenna 50 are provided on the processing chamber 12 and the window 42. The antenna 50 and the shield 60 are disposed outside the processing chamber 12 and on an upper portion of the window 42. In one embodiment, the antenna 50 includes an inner antenna element 52A and an outer antenna element 52B. The inner antenna element 52A is a spiral coil disposed in the center of the window 42. The outer antenna element 52B is a spiral coil disposed on the window 42 and on an outer periphery side of the inner antenna element 52A. The inner antenna element 52A and the outer antenna element 52B are each composed of a conductive material such as copper, aluminum, stainless steel, or the like.

[0099] The inner antenna element 52A is connected to an RF power source 70A, and the outer antenna element 52B is connected to an RF power source 70B. The inner antenna element 52A and the outer antenna element 52B each receive a power supply of the same or different frequencies from the RF power source 70A and the RF power source 70B. When RF power is supplied from the RF power source 70A or the RF power source 70B to the antenna 50, an induced magnetic field is generated in the space 12c, and processing gas in the space 12c is excited to generate plasma above the substrate W.

[0100] The etching apparatus 10 further has a controller 80. The controller 80 can also be a computing device having a processor, a storage section such as a memory, an input section, a display, and the like. The controller 80 operates based on a control program and process data stored in the storage section to control each section of the etching apparatus 10. For example, the controller 80 controls the plurality of flow controllers 44b, the plurality of valves 44c, the exhaust device 38, the RF power sources 70A, 70B, the RF power source 30, the matcher 32, the heater power source HP, and the like. The controller 80 can also control each section of the etching apparatus 10 based on the control program and the process data when implementing the etching method according to the embodiments.

[0101] It should be understood that all points of the embodiments disclosed herein are illustrative and not restrictive. The above-described embodiments can be omitted, replaced, and changed in various ways without departing from the appended claims and the spirit thereof.

[0102] For example, in the method according to the first embodiment and the second embodiment, the etching shape can be monitored after the step (d), and the first frequency and the second frequency can be adjusted. The etching shape refers to, for example, the entire shape formed on the substrate, such as the width of the recess. The monitoring device for monitoring the etching shape can be provided at any position in the etching device or in the processing system including the etching device. In one example, the monitoring device is provided at the opening 12p of the etching device 10 shown in FIG. 1. As the monitoring device, an optical observation device, a weight meter, an ultrasonic microscope, or the like can be used. Figure 12

[0103] Reference Signs

[0104] 10: etching device; 12: processing chamber; 12c: space; 12e: exhaust port; 12i: suction port; 12p: opening; 13: support mechanism; 14: substrate support table; 16: electrostatic chuck; 18: lower electrode; 18a: first plate; 18b: second plate; 22: direct current power supply; 23: switch; 24: flow path; 26a, 26b: pipe; 28: gas supply line; 30: RF power supply; 32: matcher; 34: shield; 36: pipe; 38: exhaust device; 40: partition; 42: window; 44: gas supply portion; 44a: gas source; 44b: flow rate controller; 44c: valve; 46: pipe; 48: gate valve; 50: antenna; 52A: inner antenna element; 52B: outer antenna element; 60: shield; 70A, 70B: RF power supply; 80: controller; W: substrate.​

Claims

1. An etching method characterized by, The etching method includes the following steps: (a) providing a substrate having a base layer and an etching target film formed on the base layer on a stage; (b) generating plasma from a processing gas; (c) etching the etching target film by supplying bias power having a first frequency to the stage to form a recess; and (d) changing the frequency of the bias power to a second frequency different from the first frequency to further etch the etching target film according to the aspect ratio of the recess after the step (c), In the etching method, the etching target film is continuously etched during a period from when the plasma is generated until the base layer is exposed, The second frequency is selected based on the shape of the recess corresponding to the first frequency, which is determined with reference to data representing the shape of the recess formed when the etching target film is etched to the base layer is exposed for each frequency of the bias power.

2. The etching method according to claim 1, wherein The plasma is continuously generated from the processing gas during a period from when the plasma is generated until the base layer is exposed.

3. The etching method according to claim 1 or 2, wherein The bias power is continuously supplied to the stage during a period from when the plasma is generated until the base layer is exposed.

4. The etching method according to claim 1, wherein When the shape of the recess determined in the data is a tapered shape, a frequency larger than the first frequency is selected as the second frequency.

5. The etching method according to claim 1, wherein When the shape of the recess determined in the data is a bow shape, a frequency smaller than the first frequency is selected as the second frequency.

6. The etching method according to claim 1 or 2, wherein With reference to the shape of the recess determined from the data, the step (c) is ended before the maximum value of the opening size of the recess becomes an upper limit value within an allowable range, or before the minimum value of the opening size of the recess becomes a lower limit value of the allowable range, and the step (d) is performed.

7. The etching method according to claim 1 or 2, wherein With reference to the shape of the recess determined from the data, a range of the aspect ratio in which the opening size of the recess is within an allowable range is determined, and the step (c) is ended within the determined range of the aspect ratio, and the step (d) is performed.

8. The etching method according to claim 1 or 2, wherein The aspect ratio of the recess is estimated using an elapsed time from when the step (c) is started or a state of the plasma.

9. The etching method according to claim 1 or 2, wherein After the process (d), at least one of the following processes is performed: the frequency of the bias power is changed to a frequency different from the frequency immediately before the change for further etching of the etching target film, in accordance with the aspect ratio of the recess.

10. The etching method according to claim 1 or 2, wherein The etching target film is finally etched to form a recess having an aspect ratio of 50 or more.

11. The etching method according to claim 1 or 2, wherein Further comprising a process of monitoring the etching shape after the process (d) to adjust the first frequency and / or the second frequency.

12. The etching method according to claim 1 or 2, wherein The bias power is a radio frequency bias power.

13. The etching method according to claim 12, wherein The bias power is a voltage pulse in which the magnitude of the voltage is periodically changed, The bias power is supplied to the stage in such a manner that a negative potential is generated on the substrate.

14. An etching method characterized by, Comprising the following processes: Process (a) of providing a substrate having a base layer and an etching target film formed on the base layer to a stage; Process (b) of generating plasma from a process gas; Process (c) of etching the etching target film by supplying a radio frequency bias power having a first frequency to the stage to form a recess; and Process (d) of changing the frequency of the radio frequency bias power to a second frequency larger than the first frequency to further etch the etching target film after a prescribed time has elapsed from the process (c), In the etching method, the etching target film is continuously etched during a period from when the plasma is generated to when the base layer is exposed, The first frequency is 0.1 MHz or more and 1 MHz or less, The second frequency is 1 MHz or more and 13 MHz or less, The recess formed in the etching target film finally has an aspect ratio of 50 or more, The second frequency is selected based on the shape of the recess corresponding to the first frequency, which is determined by referring to data indicating the shape of the recess formed when the etching target film is etched to the base layer is exposed for each frequency of the bias power.

15. An etching apparatus, characterized by, Having: A process chamber having a gas supply port and a gas exhaust port; A stage configured to hold a substrate in the process chamber; A radio frequency power source configured to supply a radio frequency power for generating plasma; A bias power source configured to supply a plurality of frequencies different from each other to the stage; and A control section, The control section causes each section to perform an etching method including the following processes: Process (a) of providing a substrate having a base layer and an etching target film formed on the base layer to a stage; Process (b) of generating plasma from a process gas; Process (c) of etching the etching target film by supplying a bias power having a first frequency to the stage to form a recess; and Process (d) of changing the frequency of the bias power to a second frequency larger than the first frequency to further etch the etching target film after a prescribed time has elapsed from the process (c), (d) changing the frequency of the bias power to a second frequency different from the first frequency based on the aspect ratio of the recess formed after the process (c) to further etch the etching target film, In the etching method, the etching target film is continuously etched during a period from when the plasma is generated to when the base layer is exposed, The second frequency is selected based on the shape of the recess corresponding to the first frequency, which is determined with reference to data indicating the shape of the recess formed when the etching target film is etched to the base layer is exposed for each frequency of the bias power.

16. The etching apparatus according to claim 15, wherein The bias power source is capable of changing the frequency of the bias power.

17. The etching apparatus according to claim 15 or 16, wherein The bias power source is a radio frequency bias power source configured to supply a radio frequency bias power to the stage.

18. The etching apparatus according to claim 15 or 16, wherein The bias power source is a voltage pulse power source configured to supply a voltage pulse in which the magnitude of the voltage periodically changes to the stage, The voltage pulse is supplied to the stage in a manner that generates a negative potential on the substrate.

19. The etching apparatus according to claim 15 or 16, further comprising a monitoring device configured to monitor the etching shape formed in the etching target film, The control section causes each section to perform an etching process further including a process of adjusting the first frequency and the second frequency based on the etching shape determined by the monitoring device. ​

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