WO2017170405A1 - Method for processing object to be processed - Google Patents

Abstract

In a method MT according to an embodiment of the present invention, a wafer W is provided with a layer to be etched EL and a mask layer MK4 provided on the layer to be etched EL, and the layer to be etched EL is etched as a result of removing individual atomic layers of the layer to be etched EL by repeatedly performing a sequence SQ3 including the following steps: a step ST9a in which secondary electrons are irradiated and the mask MK4 is covered with a silicon oxide compound by generating plasma and applying DC voltage to an upper electrode 30 of a parallel plate electrode; a step ST9b in which a fluorocarbon gas plasma is generated and a mixed layer MX2 including radicals is formed on the atomic layer on the surface of the layer to be etched EL; and a step ST9d in which Ar gas plasma is generated and the mixed layer MX2 is removed by applying bias voltage.

Description

Method for processing an object

Embodiments of the present invention relate to a method of processing an object to be processed, and more particularly to a method including creation of a mask.

In order to realize miniaturization of a device such as a semiconductor element, it is necessary to form a pattern having a smaller dimension than a critical dimension obtained by microfabrication using a conventional photolithography technique. Development of EUV (Extreme Ultraviolet) technology, etc., which is a next-generation exposure technology, is being promoted as a technique for forming a pattern having such dimensions. In the EUV technology, light having a remarkably shorter wavelength than that of a conventional UV light source wavelength is used. For example, light having a very short wavelength of 13.5 [nm] is used. In addition, as an alternative to conventional lithography technology, a pattern is formed using a self-assembled block copolymer (BCP), which is one of the self-assembled materials that spontaneously organize ordered patterns. Attention has been focused on the directed self-assembly (DSA) technology that forms.

When pattern etching of a narrow pattern is performed using the above EUV technology, DSA technology, or the like, the mask becomes fragile due to the narrow pattern, and the mask may collapse. In contrast, Patent Documents 1 and 2 disclose a technique for protecting a mask.

The method for enhancing the plasma etching performance disclosed in Patent Document 1 is a method for etching a structure defined by an etch mask using plasma to form features without bowing in a dielectric layer on a semiconductor wafer by etching. Is the method. In the technique of Patent Document 1, a mask is formed on a dielectric layer, a protective silicon-containing coating is formed on the exposed surface of the mask, and the feature is etched through the mask and the protective silicon-containing coating. In yet another method, this feature is partially etched prior to forming the protective silicon-containing coating. Thus, in the technique of Patent Document 1, a protective silicon-containing coating is formed using plasma on a resist mask or on a side wall of a partially etched feature, and thus formed protective silicon It has been proposed that the mask is protected by the containing coating, shrink control of CD (Critical Dimension) dimensions is performed, and bowing by etching is controlled.

The plasma etching method disclosed in Patent Document 2 is intended to prevent and suppress line wiggling and striation caused by pattern collapse after plasma etching of a silicon oxide film or the like using a multilayer resist mask. . In the technique of Patent Document 2, in a plasma etching method in which a film to be etched is plasma-etched using a multilayer resist mask, the multilayer resist mask includes an upper layer resist, an inorganic film-based intermediate film, and a lower layer resist. A sidewall protective film forming step of forming a sidewall protective film;
As described above, in the technique of Patent Document 2, in order to prevent line wiggling and striation, a side wall protective film is formed after the lower layer resist is processed on the mask of the three-layer structure. It has been proposed to prevent line wiggling and striation.

JP 2008-60566 A JP 2012-15343 A

However, in the technique of forming a protective film on the mask as in Patent Documents 1 and 2, particularly when a carbon and fluorine polymer film is formed on the mask by a CxFx-based gas used during etching of an inorganic film system, The ions can collide with the polymerized film, which can cause wiggling in the mask. Such mask bending may hinder precise pattern etching, and may also cause damage to the mask. On the other hand, when the deposition of the polymerized film is reduced, the mask is not sufficiently protected, and a situation such as a reduction in mask selectivity may occur. As described above, it is necessary to realize a technique for avoiding the bending of the mask caused by the protective film that protects the mask while protecting the mask.

In one aspect, a method for treating a workpiece is provided. The object to be processed includes a layer to be etched and a first mask provided on the layer to be etched, and the method generates plasma in a processing container of a plasma processing apparatus in which the object to be processed is accommodated. By applying a negative DC voltage to the upper electrode of the parallel plate electrode provided in the processing container, the first mask is irradiated with secondary electrons, and the upper electrode is provided with silicon from the electrode plate containing silicon. A first step of covering the first mask with a silicon oxide compound containing silicon, and generating a plasma of a first gas in a processing container after the first step is performed, A second step of forming a mixed layer containing radicals contained in the atomic layer on the surface of the layer to be etched, a third step of purging the space in the processing container after the execution of the second step, and a third step Of the process After the operation, a plasma of a second gas is generated in the processing container, a bias voltage is applied to the plasma, and the mixed layer is removed. After the execution of the fourth process, The first sequence including the fifth step of purging the space is repeatedly executed, and the etching target layer is etched by removing the etching target layer for each atomic layer.

In this way, the necessary protection for the first mask is performed each time the first sequence for removing the atomic layer on the surface of the layer to be etched is performed, and such a first sequence is repeatedly performed. Thus, the protection necessary for the etching of the etching target layer is formed on the first mask, and excessive protection can be avoided. Accordingly, the thickness of the protective film that protects the mask is sufficiently reduced, so that the mask can be prevented from being bent by the protective film.

The first gas includes a fluorocarbon-based gas and a rare gas. Thus, since the first gas contains a fluorocarbon-based gas, in the second step, fluorine radicals and carbon radicals are supplied to the surface of the layer to be etched, and a mixed layer containing both radicals is formed on the surface. Can be done.

The second gas is a rare gas. As described above, since the second gas contains a rare gas, the mixed layer formed on the surface of the etching target layer in the fourth step is separated from the surface by the energy that the rare gas plasma receives by the bias voltage. Can be removed.

Before the execution of the first sequence, the method further includes a step of forming a first mask, and the step includes a sixth step and a seventh step, and the sixth step, the seventh step, The etching process is performed using the second mask provided on the antireflection film for the organic film provided on the layer to be etched and the antireflection film provided on the organic film. Thus, the first mask is formed, the sixth step etches the antireflection film, the seventh step etches the organic film after the execution of the sixth step, and the first mask It is formed by executing the sixth step and the seventh step, and is formed from an antireflection film and an organic film.

In the sixth step, a protective film is formed conformally on the surface of the second mask in the processing container (referred to as step a), and the protective film is formed after execution of step a. A step of removing the antireflection film for each atomic layer by plasma generated in the processing container using the second mask and etching the antireflection film (referred to as step b). As described above, by performing step a, a protective film having a conformal film thickness that is accurately controlled is formed on the second mask regardless of the density difference of the mask, and the shape of the mask is maintained. However, the resistance to the etching of the mask is enhanced, and further, the step b is executed, so that the mask selection ratio is improved, and the shape of the mask (LWR (Line Width Roughness) and LER (Line Edge Roughness)) is improved by the etching. The impact is reduced.

In the sixth step, before the execution of step a, plasma is generated in the processing container and a negative DC voltage is applied to the upper electrode provided in the processing container, so that secondary electrons are applied to the second mask. It further includes an irradiation step (referred to as step c). As described above, since the secondary mask is irradiated with the secondary electrons before the execution of the step a, the second mask can be modified before the formation of the protective film. Damage can be suppressed.

In step c, plasma is generated in the processing container to apply a negative DC voltage to the upper electrode, thereby releasing silicon from the electrode plate and covering the second mask with the silicon oxide compound containing silicon. Thus, since the silicon oxide compound covers the second mask in the step c, damage to the second mask due to the subsequent steps can be further suppressed.

Step a includes an eighth step of supplying a third gas into the processing container, a ninth step of purging the space in the processing container after the execution of the eighth step, and after the execution of the ninth step. The second sequence including the tenth step of generating the plasma of the fourth gas in the processing container and the eleventh step of purging the space in the processing container after the execution of the tenth step is repeated. By executing this, a protective film is conformally formed on the surface of the second mask, and the eighth step does not generate plasma of the third gas. As described above, in step a, a protective film can be conformally formed on the surface of the second mask by a method similar to the ALD (Atomic Layer Deposition) method.

The third gas contains an organic-containing aminosilane-based gas. As described above, since the third gas contains an aminosilane-based gas containing an organic substance, a silicon reaction precursor is formed on the second mask along the atomic layer of the second mask by the eighth step. .

In one embodiment, the aminosilane-based gas of the third gas may include an aminosilane having 1 to 3 silicon atoms. The aminosilane-based gas of the third gas can include an aminosilane having 1 to 3 amino groups. As described above, aminosilane containing 1 to 3 silicon atoms can be used as the aminosilane-based gas of the third gas. In addition, aminosilane containing 1 to 3 amino groups can be used as the aminosilane-based gas of the third gas.

The fourth gas includes a gas containing oxygen atoms and carbon atoms. As described above, since the fourth gas contains oxygen atoms, in the tenth step, the oxygen atoms are oxidized on the second mask by combining with the silicon reaction precursor provided on the second mask. A protective film of silicon can be formed conformally. Further, since the fourth gas contains carbon atoms, erosion of the second mask by oxygen atoms can be suppressed by the carbon atoms.

In step b, after execution of step a, a twelfth step of generating a plasma of a fifth gas in the processing container and forming a mixed layer containing radicals contained in the plasma on the surface of the antireflection film; After the execution of the step 12, the thirteenth step of purging the space in the processing container, and after the execution of the thirteenth process, the sixth gas plasma is generated in the processing container, and a bias voltage is applied to the plasma. Then, the third sequence including the fourteenth step of removing the mixed layer and the fifteenth step of purging the space in the processing container after the execution of the fourteenth step is repeatedly executed, and the antireflection film Is removed for each atomic layer to etch the antireflection film. As described above, in the step b, the antireflection film can be removed for each atomic layer by a method similar to the ALE (Atomic Layer Etching) method.

The fifth gas includes a fluorocarbon-based gas and a rare gas. Thus, since the fifth gas contains a fluorocarbon-based gas, in the twelfth step, fluorine radicals and carbon radicals are supplied to the surface of the antireflection film, and a mixed layer containing both radicals is formed on the surface. Can be done.

The sixth gas includes a rare gas. As described above, since the sixth gas contains a rare gas, in the fourteenth step, the mixed layer formed on the surface of the antireflection film is separated from the surface by the energy that the rare gas plasma receives by the bias voltage. Can be removed.

In the seventh step, after the execution of the sixth step, the organic film is etched using the third mask by the plasma generated in the processing container, and the third mask is the sixth step. The second mask and the antireflection film are formed. As described above, the execution of the sixth step forms the third mask on the organic film with the shape maintained and the selectivity improved without depending on the density of the mask. The organic film can be etched using the mask, and the organic film can be satisfactorily etched.

As described above, it is possible to realize a technique for avoiding the mask bending caused by the protective film protecting the mask while protecting the mask.

FIG. 1 is a flow diagram illustrating a method of an embodiment. FIG. 2 is a diagram illustrating an example of a plasma processing apparatus. FIG. 3 is a cross-sectional view showing the state of the object to be processed before and after each step shown in FIG. 1 including the (a) part, the (b) part, and the (c) part. FIG. 4 is a cross-sectional view showing the state of the object to be processed after performing the steps shown in FIG. FIG. 5 is a diagram schematically showing how the protective film is formed in the sequence for forming the protective film shown in FIG. FIG. 6 is a diagram showing the principle of etching in the method shown in FIG.

Hereinafter, various embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Hereinafter, an etching method (method MT) that can be performed using the plasma processing apparatus 10 will be described with reference to FIG. FIG. 1 is a flow diagram illustrating a method of an embodiment. A method MT according to an embodiment shown in FIG. 1 is a method for processing an object to be processed (hereinafter also referred to as “wafer”). The method MT is an example of a method for etching a wafer. In the method MT of one embodiment, a series of steps can be performed using a single plasma processing apparatus.

FIG. 2 is a diagram illustrating an example of a plasma processing apparatus. FIG. 2 schematically shows a cross-sectional structure of a plasma processing apparatus 10 that can be used in various embodiments of a method for processing an object. As shown in FIG. 2, the plasma processing apparatus 10 is a plasma etching apparatus including parallel plate electrodes, and includes a processing container 12. The processing container 12 has a substantially cylindrical shape. The processing container 12 is made of, for example, aluminum, and an inner wall surface thereof is anodized. The processing container 12 is grounded for safety.

A substantially cylindrical support portion 14 is provided on the bottom of the processing container 12. The support part 14 is comprised from the insulating material, for example. The insulating material constituting the support portion 14 may contain oxygen like quartz. The support portion 14 extends in the vertical direction from the bottom of the processing container 12 in the processing container 12. A mounting table PD is provided in the processing container 12. The mounting table PD is supported by the support unit 14.

The mounting table PD holds the wafer W on the upper surface of the mounting table PD. The mounting table PD has a lower electrode LE and an electrostatic chuck ESC. The lower electrode LE includes a first plate 18a and a second plate 18b. The first plate 18a and the second plate 18b are made of a metal such as aluminum aluminum and have a substantially disk shape. The second plate 18b is provided on the first plate 18a and is electrically connected to the first plate 18a.

An electrostatic chuck ESC is provided on the second plate 18b. The electrostatic chuck ESC has a structure in which electrodes that are conductive films are arranged between a pair of insulating layers or a pair of insulating sheets. A DC power source 22 is electrically connected to the electrode of the electrostatic chuck ESC via a switch 23. The electrostatic chuck ESC attracts the wafer W with an electrostatic force such as a Coulomb force generated by a DC voltage from the DC power supply 22. Thereby, the electrostatic chuck ESC can hold the wafer W.

A focus ring FR is disposed on the peripheral edge of the second plate 18b so as to surround the edge of the wafer W and the electrostatic chuck ESC. The focus ring FR is provided in order to improve the etching uniformity. The focus ring FR is made of a material appropriately selected according to the material of the film to be etched, and can be made of, for example, quartz.

A coolant channel 24 is provided inside the second plate 18b. The refrigerant flow path 24 constitutes a temperature adjustment mechanism. Refrigerant is supplied to the refrigerant flow path 24 from a chiller unit (not shown) provided outside the processing container 12 via a pipe 26a. The refrigerant supplied to the refrigerant flow path 24 is returned to the chiller unit via the pipe 26b. Thus, the refrigerant is supplied to the refrigerant flow path 24 so as to circulate. By controlling the temperature of the refrigerant, the temperature of the wafer W supported by the electrostatic chuck ESC is controlled.

The plasma processing apparatus 10 is provided with a gas supply line 28. The gas supply line 28 supplies the heat transfer gas from the heat transfer gas supply mechanism, for example, He gas, between the upper surface of the electrostatic chuck ESC and the back surface of the wafer W.

The plasma processing apparatus 10 is provided with a heater HT that is a heating element. The heater HT is embedded in the second plate 18b, for example. A heater power source HP is connected to the heater HT. By supplying electric power from the heater power source HP to the heater HT, the temperature of the mounting table PD is adjusted, and the temperature of the wafer W mounted on the mounting table PD is adjusted. The heater HT may be built in the electrostatic chuck ESC.

The plasma processing apparatus 10 includes an upper electrode 30. The upper electrode 30 is disposed above the mounting table PD so as to face the mounting table PD. The lower electrode LE and the upper electrode 30 are provided substantially parallel to each other. A processing space S for performing plasma processing on the wafer W is provided between the upper electrode 30 and the lower electrode LE.

The upper electrode 30 is supported on the upper portion of the processing container 12 via an insulating shielding member 32. The insulating shielding member 32 is made of an insulating material and can contain oxygen, for example, quartz. The upper electrode 30 can include an electrode plate 34 and an electrode support 36. The electrode plate 34 faces the processing space S, and the electrode plate 34 is provided with a plurality of gas discharge holes 34a. In one embodiment, the electrode plate 34 contains silicon. In another embodiment, the electrode plate 34 may contain silicon oxide.

The electrode support 36 detachably supports the electrode plate 34 and can be made of a conductive material such as aluminum. The electrode support 36 may have a water cooling structure. A gas diffusion chamber 36 a is provided inside the electrode support 36. A plurality of gas flow holes 36 b communicating with the gas discharge holes 34 a extend downward from the gas diffusion chamber 36 a. The electrode support 36 is formed with a gas introduction port 36c that guides the processing gas to the gas diffusion chamber 36a, and a gas supply pipe 38 is connected to the gas introduction port 36c.

A gas source group 40 is connected to the gas supply pipe 38 via a valve group 42 and a flow rate controller group 44. The gas source group 40 has a plurality of gas sources. The plurality of gas sources includes an organic-containing aminosilane-based gas source, a fluorocarbon-based gas source (C _x F _y gas (x, y is an integer of 1 to 10)), a gas source having oxygen atoms and carbon atoms. (Eg, carbon dioxide gas), a source of nitrogen gas, a source of hydrogen-containing gas, and a source of noble gas. As the fluorocarbon-based gas, any fluorocarbon-based gas such as CF ₄ gas, C ₄ F ₆ gas, and C ₄ F ₈ gas can be used. As the aminosilane-based gas, those having a molecular structure having a relatively small number of amino groups can be used. For example, monoaminosilane (H ₃ —Si—R (R contains an organic substance and is substituted). Good amino groups)) can be used. The aminosilane-based gas (a gas contained in the gas G1 described later) can include an aminosilane that can have 1 to 3 silicon atoms, or an aminosilane that has 1 to 3 amino groups. Can be included. An aminosilane having 1 to 3 silicon atoms is a monosilane having 1 to 3 amino groups (monoaminosilane), a disilane having 1 to 3 amino groups, or a trisilane having 1 to 3 amino groups It can be. Furthermore, the above aminosilane can have an optionally substituted amino group. Furthermore, the amino group can be substituted with any of a methyl group, an ethyl group, a propyl group, and a butyl group. Further, the above methyl group, ethyl group, propyl group, or butyl group can be substituted by halogen. As the rare gas, any rare gas such as Ar gas or He gas can be used.

The valve group 42 includes a plurality of valves, and the flow rate controller group 44 includes a plurality of flow rate controllers such as a mass flow controller. Each of the plurality of gas sources of the gas source group 40 is connected to the gas supply pipe 38 via a corresponding valve of the valve group 42 and a corresponding flow rate controller of the flow rate controller group 44. Therefore, the plasma processing apparatus 10 can supply the gas from one or more gas sources selected from the plurality of gas sources of the gas source group 40 into the processing container 12 at individually adjusted flow rates. It is.

In the plasma processing apparatus 10, a deposition shield 46 is detachably provided along the inner wall of the processing container 12. The deposition shield 46 is also provided on the outer periphery of the support portion 14. The deposition shield 46 prevents the etching byproduct (depot) from adhering to the processing container 12 and can be configured by coating an aluminum material with ceramics such as Y ₂ O ₃ . In addition to Y ₂ O ₃ , the deposition shield can be made of a material containing oxygen such as quartz.

An exhaust plate 48 is provided on the bottom side of the processing container 12 and between the support 14 and the side wall of the processing container 12. The exhaust plate 48 can be configured by, for example, coating an aluminum material with ceramics such as Y ₂ O ₃ . An exhaust port 12 e is provided below the exhaust plate 48 and in the processing container 12. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 has a vacuum pump such as a turbo molecular pump, and can depressurize the space in the processing container 12 to a desired degree of vacuum. A loading / unloading port 12 g for the wafer W is provided on the side wall of the processing container 12, and the loading / unloading port 12 g can be opened and closed by a gate valve 54.

The plasma processing apparatus 10 further includes a first high frequency power source 62 and a second high frequency power source 64. The first high-frequency power source 62 is a power source that generates first high-frequency power for plasma generation, and generates a high-frequency power of 27 to 100 [MHz], in one example, 60 [MHz]. The first high frequency power supply 62 is connected to the upper electrode 30 via the matching unit 66. The matching unit 66 is a circuit for matching the output impedance of the first high-frequency power source 62 with the input impedance on the load side (lower electrode LE side). Note that the first high-frequency power source 62 may be connected to the lower electrode LE via the matching unit 66.

The second high-frequency power source 64 is a power source that generates second high-frequency power for drawing ions into the wafer W, that is, a power source for generating high-frequency bias power, and has a frequency within a range of 400 [kHz] to 40.68 [MHz]. In one example, high-frequency bias power having a frequency of 13.56 [MHz] is generated. The second high frequency power supply 64 is connected to the lower electrode LE via the matching unit 68. The matching unit 68 is a circuit for matching the output impedance of the second high-frequency power source 64 with the input impedance on the load side (lower electrode LE side).

The plasma processing apparatus 10 further includes a power source 70. The power source 70 is connected to the upper electrode 30. The power source 70 applies a voltage to the upper electrode 30 for drawing positive ions present in the processing space S into the electrode plate 34. In one example, the power source 70 is a DC power source that generates a negative DC voltage. When such a voltage is applied from the power source 70 to the upper electrode 30, positive ions existing in the processing space S collide with the electrode plate 34. Thereby, secondary electrons and / or silicon are emitted from the electrode plate 34.

In one embodiment, the plasma processing apparatus 10 may further include a control unit Cnt. The control unit Cnt is a computer including a processor, a storage unit, an input device, a display device, and the like, and controls each unit of the plasma processing apparatus 10. Specifically, the control unit Cnt includes a valve group 42, a flow rate controller group 44, an exhaust device 50, a first high-frequency power source 62, a matching unit 66, a second high-frequency power source 64, a matching unit 68, a power source 70, and a heater power source. Connected to HP and chiller unit.

The control unit Cnt operates according to a program based on the input recipe and sends out a control signal. In accordance with a control signal from the control unit Cnt, selection and flow rate of the gas supplied from the gas source group 40, exhaust of the exhaust device 50, power supply from the first high frequency power source 62 and the second high frequency power source 64, and from the power source 70 It is possible to control the voltage application, the power supply of the heater power supply HP, the refrigerant flow rate from the chiller unit, and the refrigerant temperature. Note that each step of the method MT for processing an object to be processed disclosed in this specification can be executed by operating each unit of the plasma processing apparatus 10 under the control of the control unit Cnt.

With reference to part (a) of FIG. 3, the main configuration of the wafer W prepared in step ST1 of the method MT shown in FIG. 1 will be described. FIG. 3 is a cross-sectional view showing a state of the object to be processed before and after each step shown in FIG.

As shown in part (a) of FIG. 3, the wafer W prepared in the process ST1 includes a substrate SB, an etching target layer EL, an organic film OL, an antireflection film AL, and a mask MK1 (second mask). ). The etched layer EL is provided on the substrate SB. The layer to be etched EL is a layer made of a material that is selectively etched with respect to the organic film OL, and an insulating film is used. The layer to be etched EL can be made of, for example, silicon oxide (SiO ₂ ). The etched layer EL can be made of other materials such as polycrystalline silicon.

The organic film OL is provided on the etched layer EL. The organic film OL is a layer containing carbon, for example, an SOH (spin-on hard mask) layer. The antireflection film AL is a silicon-containing antireflection film, and is provided on the organic film OL.

The mask MK1 is provided on the antireflection film AL. The mask MK1 is a resist mask made of a resist material, and is produced by patterning a resist layer by a photolithography technique. The mask MK1 can be, for example, an ArF resist. The mask MK1 partially covers the antireflection film AL. The mask MK1 defines an opening OP1 that partially exposes the antireflection film AL. The pattern of the mask MK1 is, for example, a line and space pattern, but other various patterns such as a pattern that provides a circular opening in a plan view and a pattern that provides an elliptical opening in a plan view. Can have.

The mask MK1 may be formed using a block copolymer such as polystyrene-block-polymethyl methacrylate (PS-b-PMMA), for example, and further utilizing the phase separation structure of PS and PMMA. .

Returning to FIG. 1, the description of the method MT will be continued. The following description will be given with reference to FIGS. 3, 4 and 5 together with FIG. FIG. 3 is a cross-sectional view showing a state of the object to be processed before and after each step shown in FIG. FIG. 4 is a cross-sectional view showing the state of the object to be processed after each step of the method shown in FIG. FIG. 5 is a diagram schematically showing how the protective film is formed in the sequence for forming the protective film shown in FIG.

In step ST1, a wafer W shown in FIG. 3A is prepared, and the wafer W is accommodated in the processing container 12 of the plasma processing apparatus 10 and placed on the electrostatic chuck ESC. After preparing the wafer W shown in part (a) of FIG. 3 as the wafer W shown in FIG. 2 in the process ST1, each process after the process ST2 is executed. A series of steps ST6 to ST7 (sixth step) is a step of etching the antireflection film AL.

In a process ST2 subsequent to the process ST1, the wafer W is irradiated with secondary electrons. In step ST2, plasma is generated in the processing container 12 before the execution of the sequence SQ1 (second sequence) for forming a silicon oxide protective film (protective film SX) conformally on the mask MK1 and step ST4. In this step, the negative electrode voltage is applied to the upper electrode 30 to irradiate the mask MK1 with secondary electrons.

As described above, since the mask MK1 is irradiated with secondary electrons before the series of steps SQ1 to ST4 for forming the protective film SX is performed, the mask MK1 is modified before the protective film SX is formed. Thus, damage to the mask MK1 due to subsequent processes can be suppressed.

The processing content of process ST2 is demonstrated concretely. First, a hydrogen-containing gas and a rare gas are supplied into the processing container 12, and high-frequency power is supplied from the first high-frequency power source 62, whereby plasma is generated in the processing container 12. A hydrogen-containing gas and a rare gas are supplied into the processing container 12 from a gas source selected from a plurality of gas sources in the gas source group 40. Accordingly, positive ions in the processing space S are attracted to the upper electrode 30, and the positive ions collide with the upper electrode 30. When positive ions collide with the upper electrode 30, secondary electrons are emitted from the upper electrode 30. By irradiating the wafer W with the emitted secondary electrons, the mask MK1 is modified. Further, when positive ions collide with the electrode plate 34, silicon that is a constituent material of the electrode plate 34 is emitted together with secondary electrons. The released silicon combines with oxygen released from the components of the plasma processing apparatus 10 exposed to the plasma. The oxygen is released from members such as the support portion 14, the insulating shielding member 32, and the deposition shield 46, for example. A silicon oxide compound is generated by the combination of silicon and oxygen, and the silicon oxide compound is deposited on the wafer W to cover and protect the mask MK1. As described above, in step ST2 of irradiating the mask MK1 with secondary electrons, plasma is generated in the processing container 12 to apply a negative DC voltage to the upper electrode 30, thereby irradiating the mask MK1 with secondary electrons. At the same time, silicon is released from the electrode plate 34, and the mask MK1 is covered with a silicon oxide compound containing the silicon. Then, the mask MK1 is irradiated with secondary electrons, and after the mask MK1 is covered with a silicon oxide compound, the space in the processing container 12 is purged, and the process proceeds to step ST2a.

As described above, since the silicon oxide compound covers the mask MK1 in the process ST2, damage to the mask MK1 in the subsequent process can be further suppressed.

Subsequent to step ST2, sequence SQ1, step ST5, sequence SQ2 (third sequence), and step ST7 (sequence SQ1 to step ST7) are sequentially executed. A series of steps from sequence SQ1 to step ST5 is a step in which a protective film SX of a silicon oxide film is conformally formed on the surface of the mask MK1, and a series of steps from sequence SQ2 to step ST7 are steps of sequence SQ1 to step ST5. After the series of steps, the antireflection film AL is precisely etched by removing the antireflection film AL for each atomic layer using the mask MK1 on which the protective film SX of the silicon oxide film is formed. In this way, by performing a series of steps from sequence SQ1 to step ST5, a protective film SX having a conformal film thickness that is accurately controlled is formed on the mask regardless of the density difference of the mask. Resistance to etching of the mask is enhanced while maintaining the shape of the mask, and further, the selection ratio of the mask is improved by executing a series of steps SQ2 to ST7, and the shape of the mask (LWR (Line Width Roughness) is improved. ) And LER (Line Edge Roughness)) are affected by etching.

Subsequent to step ST2, the sequence SQ1 is executed once or more. The sequence SQ1 and the step ST4 are steps for forming the silicon oxide protective film SX conformally with a uniform thickness on the wafer W by a method similar to the ALD (Atomic Layer Deposition) method, and are sequentially executed in the sequence SQ1. The process ST3a (8th process), process ST3b (9th process), process ST3c (10th process), and process ST3d (11th process) are included.

Step ST3a supplies the gas G1 (third gas) into the processing container 12. Specifically, in step ST3a, a gas G1 containing silicon is introduced into the processing container 12, as shown in part (a) of FIG. The gas G1 contains an organic-containing aminosilane-based gas. An organic-containing aminosilane-based gas G1 is supplied into the processing vessel 12 from a gas source selected from a plurality of gas sources in the gas source group 40. As the gas G1, for example, monoaminosilane (H ₃ —Si—R (where R is an organic-containing amino group)) is used as an organic-containing aminosilane-based gas. In the process ST3a, the plasma of the gas G1 is not generated.

The molecules of the gas G1 adhere to the surface of the wafer W as a reaction precursor (layer Ly1) as shown in part (b) of FIG. The molecules of gas G1 (monoaminosilane) adhere to the surface of the wafer W by chemical adsorption based on chemical bonds, and plasma is not used. In step ST3a, the temperature of the wafer W is about 0 degree Celsius or higher and not higher than the glass transition temperature of the material included in the mask MK1 (for example, 200 degree Celsius or lower). Note that a gas other than monoaminosilane can be used as long as it can be attached to the surface by chemical bonding within the temperature range and contains silicon.

As described above, since the gas G1 contains an organic-containing aminosilane-based gas, the silicon reaction precursor (layer Ly1) is formed on the mask MK1 along the atomic layer on the surface of the mask MK1 by the process ST3a.

In step ST3b subsequent to step ST3a, the space in the processing container 12 is purged. Specifically, the gas G1 supplied in step ST3a is exhausted. In step ST3b, an inert gas such as a nitrogen gas or a rare gas (eg, Ar gas) may be supplied to the processing container 12 as a purge gas. That is, the purge in the process ST3b may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation. In the process ST3b, molecules excessively attached on the wafer W can also be removed. Thus, the reaction precursor layer Ly1 is an extremely thin monomolecular layer.

In step ST3c subsequent to step ST3b, plasma P1 of gas G2 (fourth gas) is generated in the processing container 12, as shown in part (b) of FIG. The gas G2 includes a gas containing oxygen atoms and carbon atoms, and may include, for example, carbon dioxide gas. In step ST3c, the temperature of the wafer W when the plasma P1 of the gas G2 is generated is not less than 0 degrees Celsius and not more than the glass transition temperature of the material included in the mask MK1 (for example, not more than 200 degrees Celsius). A gas G2 containing a gas containing oxygen atoms and carbon atoms is supplied into the processing container 12 from a gas source selected from a plurality of gas sources of the gas source group 40. Then, high frequency power is supplied from the first high frequency power supply 62. In this case, the bias power of the second high frequency power supply 64 can be applied. It is also possible to generate plasma using only the second high frequency power supply 64 without using the first high frequency power supply 62. By operating the exhaust device 50, the pressure in the space in the processing container 12 is set to a preset pressure. In this way, the plasma P1 of the gas G2 is generated in the processing container 12.

As shown in part (b) of FIG. 5, when the plasma P1 of the gas G2 is generated, active species of oxygen and active species of carbon, for example, oxygen radicals and carbon radicals are generated, and (c) of FIG. As shown in the figure, a layer Ly2 (corresponding to the protective film SX) which is a silicon oxide film is formed as a monomolecular layer. Since the carbon radical can function to suppress oxygen erosion to the mask MK1, the silicon oxide film can be stably formed as a protective film on the surface of the mask MK1. The bond energy of the Si—O bond of the silicon oxide film is about 192 [kcal], and the bond energy of each of the C—C bond, CH bond, and CF bond (about 50-110 [kcal], 70− Therefore, the silicon oxide film can function as a protective film.

As described above, since the gas G2 contains oxygen atoms, in the step ST3c, the oxygen atoms are bonded to the silicon reaction precursor (layer Ly1) provided on the mask MK1, whereby the silicon oxide film is formed on the mask MK1. The layer Ly2 can be formed conformally. In addition, since the gas G2 contains carbon atoms, erosion of the mask MK1 by oxygen atoms can be suppressed by the carbon atoms. Accordingly, in the sequence SQ1, as in the ALD method, the silicon oxide film layer Ly2 is thinly and uniformly formed on the surface of the wafer W regardless of the density of the mask MK1 by executing the sequence SQ1 once (unit cycle). It can be formed conformally with a sufficient film thickness.

In step ST3d subsequent to step ST3c, the space in the processing container 12 is purged. Specifically, the gas G2 supplied in step ST3c is exhausted. In step ST3d, an inert gas such as nitrogen gas or a rare gas (eg, Ar) may be supplied to the processing container 12 as a purge gas. In other words, the purge in step ST3d may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation.

In step ST4 subsequent to sequence SQ1, it is determined whether or not to end execution of sequence SQ1. Specifically, in step ST4, it is determined whether or not the number of executions of the sequence SQ1 has reached a preset number. The determination of the number of executions of the sequence SQ1 is to determine the thickness of the protective film SX formed on the wafer W shown in part (b) of FIG. That is, the film thickness of the protective film SX finally formed on the wafer W is determined by the product of the film thickness of the silicon oxide film formed by executing the sequence SQ1 once (unit cycle) and the number of executions of the sequence SQ1. The thickness can be substantially determined. Therefore, the number of executions of sequence SQ1 can be set according to the desired thickness of protective film SX formed on wafer W. As described above, the sequence SQ1 is repeatedly executed, so that the protective film SX of the silicon oxide film is conformally formed on the surface of the mask MK1.

When it is determined in step ST4 that the number of executions of the sequence SQ1 has not reached the preset number (step ST4: NO), the execution of the sequence SQ1 is repeated again. On the other hand, when it is determined in step ST4 that the number of executions of sequence SQ1 has reached the preset number (step ST4: YES), the execution of sequence SQ1 is terminated. As a result, a protective film SX that is a silicon oxide film is formed on the surface of the wafer W as shown in FIG. That is, by repeating the sequence SQ1 for a preset number of times, the protective film SX having a preset thickness is conformally formed on the surface of the wafer W in a uniform film regardless of the density of the mask MK1. It is formed. The thickness of the protective film SX provided on the mask MK1 is accurately controlled by repeatedly executing the sequence SQ1.

As described above, in the series of steps SQ1 and ST4, the protective film SX can be conformally formed on the surface of the mask MK1 by a method similar to the ALD method.

The protective film SX formed by the sequence SQ1 and the series of steps ST4 includes a region R1, a region R2, and a region R3, as shown in part (b) of FIG. The region R3 is a region that extends along the side surface of the mask MK1. The region R3 extends from the surface of the antireflection film AL to the lower side of the region R1. Region R1 extends on the upper surface of mask MK1 and on region R3. The region R2 extends between the adjacent regions R3 and on the surface of the antireflection film AL. As described above, the sequence SQ1 forms the protective film SX in the same manner as the ALD method. Therefore, the film thicknesses of the region R1, the region R2, and the region R3 are substantially equal to each other regardless of the density of the mask MK1. It becomes the film thickness.

In step ST5 subsequent to step ST4, the protective film SX is etched (etched back) so as to remove the region R1 and the region R2. In order to remove the region R1 and the region R2, anisotropic etching conditions are necessary. For this reason, in step ST5, a processing gas containing fluorocarbon-based gas (C _x F _y is CF ₄ , C ₄ F ₈ , CHF ₃ ) from a gas source selected from the plurality of gas sources of the gas source group 40 is used as a processing container. 12 is supplied. Then, high-frequency power is supplied from the first high-frequency power source 62, high-frequency bias power is supplied from the second high-frequency power source 64, and the exhaust device 50 is operated to preset the pressure in the space in the processing vessel 12. Set to pressure. At this time, in order to promote anisotropic etching, a low pressure direction (20 [mT] or less) is desirable to lengthen the mean free path. In this way, a fluorocarbon-based gas plasma is generated. The active species including fluorine in the generated plasma preferentially etch the region R1 and the region R2 by being drawn in the vertical direction by the high frequency bias power. As a result, as shown in FIG. 3C, the region R1 and the region R2 are selectively removed, and the mask MS is formed by the remaining region R3. Mask MS and mask MK1 constitute mask MK2 on the surface of antireflection film AL.

Subsequent to step ST5, a series of steps of sequence SQ2 to step ST7 is executed. A series of steps from sequence SQ2 to step ST7 is a step of etching the antireflection film AL.

First, following step ST5, the sequence SQ2 is executed once or more. Sequence SQ2 is a series of precise etching of the antireflection film AL that is not covered by the mask MK2 with a high selection ratio regardless of the density of the mask MK2, by a method similar to the ALE (Atomic Layer Etching) method. Step ST6a (Twelfth step), Step ST6b (Thirteenth step), Step ST6c (Fourteenth step), Step ST6d (Fifteenth step), which are steps, which are sequentially executed in sequence SQ2.

In step ST6a, plasma of the gas G3 (fifth gas) is generated in the processing container 12, and a mixed layer MX1 containing radicals contained in the plasma is formed in the atomic layer on the surface of the antireflection film AL. In step ST6a, in a state where the wafer W is placed on the electrostatic chuck ESC, the gas G3 is supplied into the processing container 12, and plasma of the gas G3 is generated. The gas G3 is an etchant gas suitable for etching the antireflection film AL containing silicon, and includes a fluorocarbon-based gas and a rare gas, and may be, for example, C _x F _y / Ar gas. C _x F _y can be CF ₄ . Specifically, a gas G3 containing a fluorocarbon-based gas and a rare gas is supplied into the processing container 12 from a gas source selected from a plurality of gas sources in the gas source group 40. Then, high-frequency power is supplied from the first high-frequency power source 62, high-frequency bias power is supplied from the second high-frequency power source 64, and the exhaust device 50 is operated to preset the pressure in the space in the processing vessel 12. Set to pressure. In this manner, plasma of the gas G3 is generated in the processing container 12. The plasma of the gas G3 contains carbon radicals and fluorine radicals.

FIG. 6 is a diagram showing the principle of etching in the method shown in FIG. 1 (sequence SQ2 and later-described sequence SQ3). In FIG. 6, white circles (white circles) indicate atoms constituting the antireflection film AL, black circles (black circles) indicate radicals, and “+” surrounded by circles is described later. The ions of rare gas atoms (for example, Ar atom ions) contained in the gas G4 (sixth gas) of FIG. As shown in part (a) of FIG. 6, carbon radicals and fluorine radicals contained in the plasma of the gas G3 are supplied to the surface of the antireflection film AL by the process ST6a. In this way, the mixed layer MX1 including the atoms constituting the antireflection film AL, the carbon radical, and the fluorine radical is formed on the surface of the antireflection film AL by the process ST6a. (See FIG. 3 (c) as well as FIG. 6 (a)).

As described above, since the gas G3 contains a fluorocarbon-based gas, in step ST6a, fluorine radicals and carbon radicals are supplied to the atomic layer on the surface of the antireflection film AL, and the mixed layer contains both radicals in the atomic layer. MX1 can be formed.

In the ArF resist mask MK1, Si of the mask MS included in the mask MK2 and carbon radicals included in the plasma of the gas G3 function as a protective film. Further, the adjustment of the fluorine radical amount can be controlled by a DC voltage from the power source 70.

In step ST6b subsequent to step ST6a, the space in the processing container 12 is purged. Specifically, the gas G3 supplied in step ST6a is exhausted. In step ST6b, an inert gas such as nitrogen gas or a rare gas (eg, Ar gas) may be supplied to the processing container 12 as a purge gas. In other words, the purge in step ST6b may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation.

In step ST6c subsequent to step ST6b, a plasma of gas G4 is generated in the processing container 12, and a bias voltage is applied to the plasma to remove the mixed layer MX1. The gas G4 includes a rare gas, and may include, for example, Ar gas. Specifically, a gas G4 containing a rare gas (for example, Ar gas) is supplied from a gas source selected from a plurality of gas sources in the gas source group 40 into the processing container 12, and high-frequency power is supplied from the first high-frequency power source 62. Is supplied, high frequency bias power is supplied from the second high frequency power supply 64, and the exhaust device 50 is operated to set the pressure in the space in the processing container 12 to a preset pressure. In this manner, plasma of the gas G4 is generated in the processing container 12. The ions (for example, Ar atoms) of the gas G4 in the generated plasma collide with the mixed layer MX1 on the surface of the antireflection film AL by being drawn in the vertical direction by the high frequency bias power, and the mixed layer MX1. To supply energy. As shown in part (b) of FIG. 6, energy is supplied to the mixed layer MX1 formed on the surface of the antireflection film AL through ions of the atoms of the gas G4 by the process ST6c. The mixed layer MX1 can be removed from the AL.

As described above, since the gas G4 contains a rare gas, in step ST6c, the mixed layer MX1 formed on the surface of the antireflection film AL is removed from the surface by the energy received by the rare gas plasma by the bias voltage. Can be done.

In step ST6d subsequent to step ST6c, the space in the processing container 12 is purged. Specifically, the gas G4 supplied in step ST6c is exhausted. In step ST6d, an inert gas such as nitrogen gas or a rare gas (eg, Ar gas) may be supplied to the processing container 12 as a purge gas. In other words, the purge in step ST6d may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation. As shown in part (c) of FIG. 6, the atoms constituting the mixed layer on the surface of the antireflection film AL and excess ions (for example, Ar atoms) contained in the plasma of the gas G4 by the purging performed in the step ST6c. Ion) can also be sufficiently removed.

In step ST7 subsequent to sequence SQ2, it is determined whether or not to end execution of sequence SQ2. Specifically, in step ST7, it is determined whether or not the number of executions of the sequence SQ2 has reached a preset number. The determination of the number of executions of the sequence SQ2 is to determine the degree of etching (depth) for the antireflection film AL. The sequence SQ2 can be repeatedly executed so as to etch the antireflection film AL up to the surface of the organic film OL. That is, the execution of the sequence SQ2 is performed so that the product of the thickness of the antireflection film AL etched by the execution of the sequence SQ2 once (unit cycle) and the number of executions of the sequence SQ2 is the total thickness of the antireflection film AL itself. The number of times can be determined. Therefore, the number of executions of the sequence SQ2 can be set according to the thickness of the antireflection film AL.

If it is determined in step ST7 that the number of executions of the sequence SQ2 has not reached the preset number (step ST7: NO), the execution of the sequence SQ2 is repeated again. On the other hand, when it is determined in step ST7 that the number of executions of sequence SQ2 has reached the preset number (step ST7: YES), the execution of sequence SQ2 is ended. Thereby, as shown in FIG. 4A, the antireflection film AL is etched to form a mask ALM. That is, by repeating the sequence SQ2 for a preset number of times, the antireflection film AL has the same and uniform width as the opening OP2 provided by the mask MK2 regardless of the density of the mask MK2 (the density of the mask MK1). Etching is performed with a wide width, and the selectivity is improved.

The mask ALM provides an opening OP3 together with the mask MK2. The opening OP3 has the same width as the width of the opening OP2 provided by the mask MK2 (see the part (c) in FIG. 3). The mask MK2 and the mask ALM constitute a mask MK3 (third mask) for the organic film OL. The width of the opening OP3 formed by etching the antireflection film AL is accurately controlled by repeatedly executing the sequence SQ2.

Further, since the silicon oxide film having a uniform and accurately controlled film thickness is formed on the side surface of the mask MK2 on the antireflection film AL through a series of steps up to step ST5, the sequence SQ2 for the antireflection film AL is performed. The influence on the shape (LWR and LER) of the mask MK2 due to the etching can be reduced. Thus, since the influence of the shape of the mask MK2 on the etching of the sequence SQ2 can be reduced, the width of the opening OP3 formed by the etching can also reduce the influence of the etching on the sequence SQ2, and the density of the mask MK2 (the density of the mask MK1) ) Can also be reduced.

As described above, a series of steps SQ2 to ST7 is performed after the step of conformally forming the silicon oxide film (region R3 (mask MS) of the protective film SX) on the surface of the mask MK1 (in step ST5). The antireflection film AL is performed by repeatedly executing the sequence SQ2 using the mask MK1 (mask MK2) on which the mask MS is formed and removing the antireflection film AL for each atomic layer. This is a process for precisely etching. Therefore, in a series of steps from sequence SQ2 to step ST7, the antireflection film AL can be removed for each atomic layer by a method similar to the ALE method.

Step ST7: In step ST8 (seventh step) subsequent to YES, the organic film OL is etched. In step ST8, after execution of the sequence SQ1 to step ST7 for performing the etching process on the antireflection film AL (after step ST7: YES), the plasma generated in the processing container 12 is used to form the organic film OL using the mask MK3. This is a step of performing an etching process. The mask MK3 is formed from the antireflection film AL in the step of etching the antireflection film AL (sequence SQ1 to step ST7).

The process of step ST8 will be specifically described. First, a processing gas containing nitrogen gas and hydrogen-containing gas is supplied into the processing container 12 from a gas source selected from among a plurality of gas sources in the gas source group 40. As the gas, a processing gas containing oxygen may be used. Then, high-frequency power is supplied from the first high-frequency power source 62, high-frequency bias power is supplied from the second high-frequency power source 64, and the exhaust device 50 is operated to set the pressure in the space in the processing container 12 to a predetermined pressure. Set. Thereby, plasma of a processing gas containing nitrogen gas and hydrogen-containing gas is generated. Hydrogen radicals, which are active species of hydrogen in the generated plasma, etch the region exposed from the mask MK3 in the entire region of the organic film OL. As a result, as shown in FIG. 4B, the organic film OL is etched, so that the opening OP4 having the same width as the width of the opening OP3 provided by the mask MK3 (see FIG. 4A) is formed. A mask OLM is formed from the organic film OL. The mask ALM and the mask OLM constitute a mask MK4 (first mask) for the layer to be etched EL. The sequence SQ2 improves the uniformity of the width of the opening OP3 of the mask MK3 regardless of the density of the mask MK3 (the density of the mask MK2), and the shape of the mask MK3 (LWR and LER) is also good. The uniformity of the width of the opening OP4 of the mask MK4 is also improved regardless of the density of the mask MK4 (the density of the mask MK3), and the shape (LWR and LER) of the mask MK4 is improved.

As described above, by executing the series of steps ST2 to ST7, the mask MK3 whose shape is maintained and the selection ratio is improved is formed on the organic film OL without depending on the density of the mask. The organic film OL can be etched by the mask MK3 having a good shape, and the organic film OL can be etched well.

Subsequent to step ST18, sequence SQ3 (first sequence) and step ST10 are executed. Sequence SQ3 and step ST10 are a series of steps for etching the layer to be etched EL by removing the layer to be etched EL for each atomic layer. The sequence SQ3 includes a process ST9a (first process), a process ST9b (second process), a process ST9c (third process), a process ST9d (fourth process), and a process ST9 (fifth process). .

In step ST9a, secondary electrons are applied to the mask MK4 by generating plasma in the processing container 12 of the plasma processing apparatus 10 and applying a negative DC voltage to the upper electrode 30 of the parallel plate electrode provided in the processing container 12. In addition, the mask MK4 is covered with a silicon oxide compound containing silicon by discharging silicon from the electrode plate 34 included in the upper electrode 30 and containing silicon. After the mask MK4 is covered with the silicon oxide compound, the space in the processing container 12 is purged, and then the process proceeds to step ST9b.

The processing content of process ST9a is demonstrated concretely. First, a hydrogen-containing gas and a rare gas (for example, Ar gas) are supplied into the processing container 12, and high-frequency power is supplied from the first high-frequency power source 62, thereby generating plasma in the processing container 12. A hydrogen-containing gas and a rare gas (for example, Ar gas) are supplied into the processing container 12 from a gas source selected from the plurality of gas sources in the gas source group 40. Accordingly, positive ions in the processing space S are attracted to the upper electrode 30, and the positive ions collide with the upper electrode 30. When positive ions collide with the upper electrode 30, secondary electrons are emitted from the upper electrode 30. By irradiating the wafer W with the emitted secondary electrons, the mask MK1 is modified. Further, when positive ions collide with the electrode plate 34, silicon that is a constituent material of the electrode plate 34 is emitted together with secondary electrons. The released silicon combines with oxygen released from the components of the plasma processing apparatus 10 exposed to the plasma. The oxygen is released from members such as the support portion 14, the insulating shielding member 32, and the deposition shield 46, for example. A silicon oxide compound is generated by the combination of silicon and oxygen, and the silicon oxide compound is deposited on the wafer W to cover and protect the mask MK4. Then, the mask MK4 is irradiated with secondary electrons, and after the mask MK4 is covered with a silicon oxide compound, the space in the processing container 12 is purged, and the process proceeds to step ST9b.

As described above, in step ST9a, plasma is generated in the processing container 12 to apply a negative DC voltage to the upper electrode 30, thereby irradiating the mask MK4 with secondary electrons and releasing silicon from the electrode plate 34. Then, the mask MK4 is covered with a silicon oxide compound containing silicon. Therefore, in the process ST9a, the silicon oxide compound covers the mask MK4, so that damage to the mask MK4 in the subsequent process can be suppressed.

In step ST9b subsequent to step ST9a, plasma of gas G5 (first gas) is generated in the processing container 12 by the same method as in step ST6a, and the mixed layer MX2 containing radicals contained in the plasma is formed as an etching target layer. It is formed in the atomic layer on the surface of EL. In step ST9b, in a state where the wafer W is placed on the electrostatic chuck ESC, the gas G5 is supplied into the processing container 12, and plasma of the gas G5 is generated. The gas G5 is an etchant gas suitable for etching the layer to be etched EL, and includes a fluorocarbon-based gas and a rare gas, and may be, for example, C _x F _y / Ar gas. C _x F _y can be CF ₄ . Specifically, a gas G5 containing a fluorocarbon-based gas and a rare gas is supplied into the processing container 12 from a gas source selected from a plurality of gas sources in the gas source group 40. Then, high-frequency power is supplied from the first high-frequency power source 62, high-frequency bias power is supplied from the second high-frequency power source 64, and the exhaust device 50 is operated to preset the pressure in the space in the processing vessel 12. Set to pressure. In this manner, plasma of the gas G5 is generated in the processing container 12. The plasma of the gas G5 contains carbon radicals and fluorine radicals. By the step ST9b, a mixed layer MX2 containing carbon radicals and fluorine radicals is formed on the atomic layer on the surface of the layer to be etched EL (see FIG. 4 (b) together with FIG. 6 (a)). Therefore, since the gas G5 contains a fluorocarbon-based gas, in step ST9b, fluorine radicals and carbon radicals are supplied to the atomic layer on the surface of the etched layer EL, and a mixed layer MX2 containing both radicals is formed in the atomic layer. Can be done.

In step ST9c subsequent to step ST9b, the space in the processing container 12 is purged by the same method as in step ST6b. Specifically, the gas G5 supplied in step ST9b is exhausted. In step ST9c, an inert gas such as nitrogen gas or a rare gas (eg, Ar gas) may be supplied to the processing container 12 as a purge gas. That is, the purge in step ST9c may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation.

In a process ST9d subsequent to the process ST9c, a plasma of the gas G6 (second gas) is generated in the processing container 12 by the same method as in the process ST6c, and a bias voltage is applied to the plasma to remove the mixed layer MX2. To do. The gas G6 includes a rare gas, and may include, for example, Ar gas. Specifically, a gas G6 containing a rare gas (for example, Ar gas) from a gas source selected from among a plurality of gas sources in the gas source group 40 is supplied into the processing container 12, and high-frequency power is supplied from the first high-frequency power source 62. Is supplied, high frequency bias power is supplied from the second high frequency power supply 64, and the exhaust device 50 is operated to set the pressure in the space in the processing container 12 to a preset pressure. In this way, plasma of the gas G6 is generated in the processing container 12. The ions of the atoms of the gas G6 in the generated plasma (for example, ions of Ar atoms) collide with the mixed layer MX2 on the surface of the layer EL to be etched by being drawn in the vertical direction by the high frequency bias power, and the mixed layer MX2 To supply energy. As shown in part (b) of FIG. 6, energy is supplied to the mixed layer MX2 formed on the surface of the etched layer EL through ions of the gas G6 by the process ST6c. The mixed layer MX2 can be removed from the EL.

As described above, since the gas G6 includes a rare gas, in step ST9d, the mixed layer MX2 formed on the surface of the etching target layer EL is removed from the surface by the energy received by the plasma of the rare gas by the bias voltage. Can be done.

In step ST9e subsequent to step ST9d, the space in the processing container 12 is purged by the same method as in step ST6d. Specifically, the gas G6 supplied in step ST9d is exhausted. In step ST9e, an inert gas such as nitrogen gas or a rare gas (eg, Ar gas) may be supplied to the processing container 12 as a purge gas. That is, the purge in step ST9e may be either a gas purge for flowing an inert gas into the processing container 12 or a purge by evacuation. As shown in part (c) of FIG. 6, excess ions contained in the plasma of the gas G6 and atoms constituting the mixed layer MX2 on the surface of the etching target EL by the purge performed in the step ST9e (for example, Ar) Atomic ions) can also be sufficiently removed. Therefore, in the series of steps from sequence SQ3 to step ST10, the layer to be etched EL can be removed for each atomic layer by the same method as ALE.

In step ST10 subsequent to sequence SQ3, it is determined whether or not to end execution of sequence SQ3 by the same method as in step ST7. Specifically, in step ST10, it is determined whether or not the number of executions of the sequence SQ3 has reached a preset number. The determination of the number of executions of the sequence SQ3 is to determine the degree (depth) of etching with respect to the etching target layer EL. The sequence SQ3 can be repeatedly executed so as to etch the etching target layer EL up to the surface of the substrate SB. That is, the execution of the sequence SQ3 is performed so that the product of the thickness of the etched layer EL etched by the execution of the sequence SQ3 once (unit cycle) and the number of executions of the sequence SQ3 becomes the total thickness of the etched layer EL itself. The number of times can be determined. Therefore, the number of executions of the sequence SQ3 can be set according to the thickness of the etched layer EL.

When it is determined in step ST10 that the number of executions of sequence SQ3 has not reached the preset number (step ST10: NO), the execution of sequence SQ3 is repeated again. On the other hand, when it is determined in step ST10 that the number of executions of sequence SQ3 has reached the preset number (step ST10: YES), the execution of sequence SQ3 is terminated. As a result, the etched layer EL is etched as shown in FIG. That is, the sequence SQ3 is repeated a predetermined number of times, so that the layer to be etched EL does not depend on the density of the mask MK4 (the density of the mask MK1), but the opening OP4 (FIG. 4B). Etching is performed with the same and uniform width as the width of (see ()), and the selectivity is improved. The width of the opening OP4 formed by etching the layer to be etched EL is accurately controlled by repeatedly executing the sequence SQ3.

Since the silicon oxide compound is formed on the side surface of the mask MK4 on the etched layer EL in step ST9a, the influence of the shape (LWR and LER) of the mask MK4 due to the etching of the sequence SQ3 on the etched layer EL can be reduced. Since the influence of the shape of the mask MK4 on the etching of the sequence SQ3 can be reduced in this way, the width of the opening OP4 formed by the etching can also reduce the influence of the etching of the sequence SQ3, and the density of the mask MK4 (the density of the mask MK1) ) Can also be reduced.

As described above, every time the sequence SQ3 for removing the atomic layer on the surface of the etched layer EL is executed, the necessary protection for the mask MK4 is performed, and the sequence SQ3 is repeatedly executed, whereby Excessive protection can be avoided while the necessary protection against the etching of the layer EL is formed in the mask MK4. Therefore, since the film thickness of the protective film that protects the mask MK4 is sufficiently reduced, the dripping of the mask MK4 caused by the protective film can be avoided.

In Step ST9b, when the gas G5 includes, for example, CF ₄ and Ar, the more the Ar gas flow rate is higher than the CF ₄ gas flow rate, the more time the Ar gas is supplied into the processing container 12. Is longer than the time for supplying the CF ₄ gas into the processing container 12, the LWR is reduced, and the shape of the mask MK4 is better maintained. Further, in the case where Ar gas is used as a rare gas used for releasing secondary electrons and silicon in the process ST9a, the longer the time for supplying the Ar gas to the processing container 12 (the implementation time of the process ST9a), the lower the LWR. The shape maintenance of the mask MK4 becomes good.

While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims. For example, in order to etch the antireflection film AL, a series of steps ST2 to ST7 is provided. However, the antireflection film AL is etched without performing the series of steps ST2 to ST7 or the sequence SQ2 The etching can be performed by a known RIE (Reactive Ion Etching) without performing the series of steps of the step ST7. Of the series of steps ST2 to ST7, for example, the step ST2 may not be performed, and the sequence SQ1 to step ST5 may not be performed.

DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus, 12 ... Processing container, 12e ... Exhaust port, 12g ... Carry-in / out port, 14 ... Support part, 18a ... 1st plate, 18b ... 2nd plate, 22 ... DC power supply, 23 ... Switch, 24 ... Refrigerant Flow path, 26a ... pipe, 26b ... pipe, 28 ... gas supply line, 30 ... upper electrode, 32 ... insulating shielding member, 34 ... electrode plate, 34a ... gas discharge hole, 36 ... electrode support, 36a ... gas diffusion Chamber 36b ... Gas flow hole 36c ... Gas inlet port 38 ... Gas supply pipe 40 ... Gas source group 42 ... Valve group 44 ... Flow controller group 46 ... Depot shield 48 ... Exhaust plate 50 DESCRIPTION OF SYMBOLS ... Exhaust device, 52 ... Exhaust pipe, 54 ... Gate valve, 62 ... 1st high frequency power supply, 64 ... 2nd high frequency power supply, 66 ... Matching device, 68 ... Matching device, 70 ... Power supply, AL ... Antireflection film, ALM ... mask, nt ... control unit, EL ... layer to be etched, ESC ... electrostatic chuck, FR ... focus ring, G1 ... gas, HP ... heater power supply, HT ... heater, LE ... lower electrode, Ly1 ... layer, Ly2 ... layer, MK1 ... Mask, MK2 ... Mask, MK3 ... Mask, MK4 ... Mask, MS ... Mask, MX1 ... Mixed layer, MX2 ... Mixed layer, OL ... Organic film, OLM ... Mask, OP1 ... Opening, OP2 ... Opening, OP3 ... Opening, OP4 ... Opening, P1 ... Plasma, PD ... Place, R1 ... Area, R2 ... Area, R3 ... Area, S ... Processing space, SB ... Substrate, SX ... Protective film, W ... Wafer.

Claims (16)

A method for processing a workpiece,
The object to be processed includes an etching target layer and a first mask provided on the etching target layer,
The method is
The first mask is formed by generating a plasma in a processing container of a plasma processing apparatus in which the object to be processed is stored and applying a negative DC voltage to an upper electrode of parallel plate electrodes provided in the processing container. Irradiating secondary electrons to the first electrode, and discharging the silicon from the electrode plate included in the upper electrode and covering the first mask with a silicon oxide compound containing the silicon; and
After the execution of the first step, a second gas plasma is generated in the processing container, and a mixed layer containing radicals contained in the plasma is formed in an atomic layer on the surface of the layer to be etched. Process,
A third step of purging the space in the processing container after the execution of the second step;
A fourth step of generating a plasma of a second gas in the processing container after the execution of the third step, applying a bias voltage to the plasma, and removing the mixed layer;
A fifth step of purging the space in the processing container after the execution of the fourth step;
Repetitively executing a first sequence including: etching the layer to be etched by removing the layer to be etched for each atomic layer;
Method. The first gas includes a fluorocarbon-based gas and a rare gas.
The method of claim 1. The second gas is a noble gas.
The method according to claim 1 or claim 2. Before the execution of the first sequence, further comprising forming the first mask;
The step of forming the first mask includes a sixth step and a seventh step. In the sixth step and the seventh step, the organic material provided on the layer to be etched is provided. The first mask is formed by performing an etching process using the second mask provided on the antireflection film with respect to the film and the antireflection film provided on the organic film,
In the sixth step, the antireflection film is etched,
In the seventh step, after the execution of the sixth step, the organic film is etched,
The first mask is formed by executing the sixth step and the seventh step, and is formed from the antireflection film and the organic film.
The method according to any one of claims 1 to 3. The sixth step includes
Forming a protective film conformally on the surface of the second mask in the processing container; and
After performing the step of forming the protective film conformally, the antireflection film is formed for each atomic layer by plasma generated in the processing container using the second mask on which the protective film is formed. Removing and etching the antireflection film;
Comprising
The method of claim 4. The sixth step includes
Before performing the step of forming the protective film conformally, plasma is generated in the processing container to apply a negative DC voltage to the upper electrode provided in the processing container, thereby A step of irradiating the mask with secondary electrons;
The method of claim 5. In the step of irradiating the second mask with secondary electrons, plasma is generated in the processing container to apply a negative DC voltage to the upper electrode, thereby releasing silicon from the electrode plate and Covering the second mask with a silicon oxide compound containing silicon;
The method of claim 6. The step of forming the protective film conformally includes:
An eighth step of supplying a third gas into the processing vessel;
A ninth step of purging the space in the processing container after the execution of the eighth step;
A tenth step of generating a plasma of a fourth gas in the processing container after the execution of the ninth step;
An eleventh step of purging the space in the processing container after the execution of the tenth step;
The protective film is conformally formed on the surface of the second mask by repeatedly executing a second sequence including:
The eighth step does not generate plasma of the third gas;
The method according to any one of claims 5 to 7. The third gas includes an organic-containing aminosilane-based gas.
The method of claim 8. The method according to claim 9, wherein the aminosilane-based gas of the third gas includes aminosilane having 1 to 3 silicon atoms. The method according to claim 9 or 10, wherein the aminosilane-based gas of the third gas includes aminosilane having 1 to 3 amino groups. The fourth gas includes a gas containing oxygen atoms and carbon atoms.
10. A method according to claim 8 or claim 9. The step of etching the antireflection film comprises the steps of:
After execution of the step of forming the protective film conformally, a plasma of a fifth gas is generated in the processing container, and a mixed layer containing radicals contained in the plasma is formed on the atomic layer on the surface of the antireflection film. A twelfth step of forming
A thirteenth step of purging the space in the processing container after the execution of the twelfth step;
After the execution of the thirteenth step, a fourteenth step of generating a plasma of a sixth gas in the processing container, applying a bias voltage to the plasma, and removing the mixed layer;
A fifteenth step of purging the space in the processing container after the execution of the fourteenth step;
Repeatedly performing a third sequence including: etching the antireflection film by removing the antireflection film for each atomic layer;
The method according to any one of claims 5 to 12. The fifth gas includes a fluorocarbon-based gas and a rare gas.
The method of claim 13. The sixth gas includes a rare gas;
15. A method according to claim 13 or claim 14. In the seventh step, after the execution of the sixth step, the plasma generated in the processing container is used to etch the organic film using a third mask,
The third mask is formed from the second mask and the antireflection film in the sixth step.
The method according to any one of claims 4 to 15.

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