JP2018098480A - Method for selectively etching first region formed from silicon nitride rather than second region formed from silicon oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the production of a deposit and achieve a high selection ratio in selectively etching a first region formed from silicon nitride rather than a second region formed from silicon oxide.SOLUTION: The method according to an embodiment hereof comprises the steps of: preparing a workpiece having first and second regions in a chamber provided by a chamber main body of a plasma processing device; generating plasma of a first gas including a hydrogen-containing gas in the chamber so as to allow active species of hydrogen to quality-modify part of the first region to form a quality-modified region; and generating plasma of a second gas including a fluorine-containing gas in the chamber so as to allow active species of fluorine to remove the quality-modified region.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present disclosure relate to a method of selectively etching a first region formed from silicon nitride with respect to a second region formed from silicon oxide.

  In manufacturing an electronic device such as a semiconductor device, it may be required to selectively etch one of two regions formed from different materials with respect to the other region. For example, it may be required to selectively etch a first region formed from silicon nitride relative to a second region formed from silicon oxide.

  In order to selectively etch the first region formed of silicon nitride with respect to the second region formed of silicon oxide, plasma etching using a hydrofluorocarbon gas is generally performed. In plasma etching using hydrofluorocarbon gas, the second region is protected by the fluorocarbon deposit, and the first region is etched by active species in the plasma. Such plasma etching is described in Patent Document 1.

JP 2003-229418 A

  In the selective etching of the first region formed of silicon nitride with respect to the second region formed of silicon oxide, a higher selection ratio is required than plasma etching using hydrofluorocarbon gas.

  In addition, since the plasma etching using hydrofluorocarbon gas protects the second region using the deposit as described above, when the etching of the first region proceeds and a narrow opening is formed, the opening becomes a deposit. And the etching of the first region may stop.

  Therefore, it is desired to suppress the generation of deposits and obtain a high selection ratio by selectively etching the first region formed from silicon nitride with respect to the second region formed from silicon oxide. It has been.

  In one aspect, a method is provided for selectively etching a first region formed from silicon nitride relative to a second region formed from silicon oxide. The method comprises the steps of (i) providing a workpiece having a first region and a second region in a chamber provided by a chamber body of a plasma processing apparatus; and (ii) the first region depending on the active species of hydrogen. A step of generating a plasma of a first gas containing a gas containing hydrogen (hereinafter referred to as a “reforming step”) in a chamber so as to reform a part to form a reformed region; and (iii) Generating a plasma of a second gas including a gas containing fluorine in the chamber so as to remove the modified region by the active species of fluorine (hereinafter referred to as “removing step”).

  In the method according to the aspect, a part of the first region is reformed by the active species of hydrogen generated in the reforming step, and the reformed region can be easily removed by the active species of fluorine. On the other hand, since the second region formed of silicon oxide is stable, it is not modified by the active species of hydrogen. Therefore, in the removal step, the modified region is selectively removed with respect to the second region. Therefore, according to this method, the first region is selectively etched with respect to the second region. In addition, the active species in the plasma generated in the reforming step and the removing step have a considerably lower deposition property or substantially more deposition property than the active species in the plasma of the hydrofluorocarbon gas. I don't have it. Therefore, according to this method, the generation of deposits is suppressed.

  In one embodiment, the workpiece is mounted in a chamber on a stage that includes an electrode that can be supplied with a high frequency for drawing ions into the workpiece, ie, a high frequency for biasing. In one embodiment, in the reforming step, a high frequency for bias is supplied to the electrode. According to this embodiment, the modification of the first region is performed more efficiently. In one embodiment, a high frequency for bias is not supplied to the electrode in the step of generating the plasma of the second gas. That is, in this embodiment, the modified region is removed not by ion sputter etching but by a chemical reaction between the modified region and the fluorine active species.

In one embodiment, the second gas may include NF ₃ gas as a gas containing fluorine.

  In one embodiment, the second gas may further include hydrogen. The ratio of the number of hydrogen atoms in the second gas to the number of fluorine atoms in the second gas is 8/9 or more. According to the plasma of the second gas, the etching selectivity of the first region is further improved.

In one embodiment, the second gas includes NF ₃ gas as a gas containing fluorine, and may further include H ₂ gas.

In one embodiment, the ratio of the flow rate of H ₂ gas in the _second gas to the flow rate of NF ₃ gas in the _second gas is 3/4 or more. According to the plasma of the second gas, the etching selectivity of the first region is further improved.

In one embodiment, the first gas includes H ₂ gas as a gas containing hydrogen.

  In one embodiment, a plurality of sequences each including a reforming step and a removing step may be executed in order.

  In one embodiment, the workpiece further includes a third region formed from silicon. The first gas may further contain a gas containing oxygen. In the modification step of this embodiment, the surface of the third region is oxidized by the active species of oxygen in the first gas, and the etching of the third region is suppressed in the etching by the removal step. Accordingly, the first region is selectively etched with respect to the second region and the third region. In one embodiment, the first region may be provided so as to cover the second region and the third region.

  In one embodiment, a plurality of sequences each including a reforming step and a removing step are executed in sequence. The workpiece further includes a third region formed from silicon. Before the execution of the plurality of sequences, the first area is provided so as to cover the second area and the third area. The plurality of sequences includes one or more first sequences and one or more second sequences. The one or more first sequences are one or more sequences that are executed immediately before the third region is exposed or until the third region is exposed, among the plurality of sequences. The one or more second sequences are one or more sequences executed after the one or more first sequences among the plurality of sequences, and are executed to oxidize the surface of the third region. In at least one or more second sequences, the first gas further includes a gas containing oxygen. In the modification step of this embodiment, the surface of the third region is oxidized, and the etching of the third region is suppressed in the etching by the removal step. Therefore, according to this embodiment, the first region is selectively etched with respect to the second region and the third region.

  In the one or more first sequences, the first gas may not include a gas containing oxygen. The plurality of sequences may further include one or more third sequences. The one or more third sequences are one or more sequences executed after the one or more second sequences among the plurality of sequences. In only one or more third sequences, or in one or more third sequences in addition to one or more first sequences, the first gas may not include a gas containing oxygen.

  In one embodiment, the ratio of the flow rate of the gas containing oxygen in the first gas to the flow rate of the gas containing hydrogen in the first gas is 3/100 or more and 9/100 or less. According to this embodiment, the first region can be etched with a higher selectivity than the third region.

In one embodiment, the gas containing oxygen may be O ₂ gas.

  As described above, by selectively etching the first region formed of silicon nitride with respect to the second region formed of silicon oxide, the generation of deposits is suppressed and a high selectivity is achieved. Can be obtained.

5 is a flow diagram illustrating a method according to one embodiment. It is sectional drawing which expands and shows a part of workpiece of an example to which the method concerning one Embodiment can be applied. It is sectional drawing which expands and shows a part of workpiece of another example in which the method concerning one Embodiment can be applied. 1 schematically illustrates a plasma processing apparatus that can be used in methods according to various embodiments. FIG. FIG. 5A is a diagram for explaining a process ST1 of the method according to the embodiment, and FIG. 5B is a state of the workpiece after execution of the process ST1 of the method according to the embodiment. FIG. 6A is a diagram for explaining a process ST2 of the method according to the embodiment, and FIG. 6B is a state of the workpiece after the process ST2 of the method according to the embodiment is performed. FIG. 6C is a diagram illustrating a state of the workpiece at the end of the method according to the embodiment. FIG. 7A is a diagram illustrating a state of the workpiece after execution of step ST1 of the method according to the embodiment, and FIG. 7B is after execution of step ST2 of the method according to the embodiment. FIG. 7C is a diagram showing the state of the workpiece at the end of the method according to the embodiment. 6 is a flowchart illustrating a method according to another embodiment. FIGS. 9A and 9B are diagrams for explaining the process ST1 in the first sequence and the process ST1 in the second sequence in the first example of the method shown in FIG. 9 (c) is a diagram showing a state in which the surface of the third region is oxidized by the execution of the step ST1 in the second sequence. FIG. 10A and FIG. 10B are diagrams for explaining the process ST1 in the first sequence and the process ST1 in the second sequence in the second example of the method shown in FIG. 10 (c) is a diagram showing a state in which the surface of the third region is oxidized by the execution of the step ST1 in the second sequence. 6 is a flowchart illustrating a method according to still another embodiment. 12 (a), FIG. 12 (b), and FIG. 12 (c) are respectively the first sequence step ST1, the second sequence step ST1, and the third sequence step in the method shown in FIG. It is a figure for demonstrating ST1. FIG. 13A, FIG. 13B, and FIG. 13C are graphs showing the results of the first experiment. FIGS. 14A and 14B are graphs showing the results of the second experiment. It is a graph which shows the result of a 2nd experiment. FIG. 16A is a diagram for explaining the reduction amount obtained for each sample in the third experiment, and FIG. 16B shows the reduction amount obtained for each sample in the third experiment. It is a table | surface which shows. 6 is a flowchart illustrating a method according to still another embodiment. It is a partially expanded sectional view of the workpiece to which the method shown in FIG. 17 is applied. FIG. 18 is a cross-sectional view showing a part of the workpiece during execution of the method shown in FIG. 17. FIG. 18 is a cross-sectional view showing a state of a part of the workpiece during execution of the method shown in FIG. 17. FIG. 18 is a cross-sectional view showing a state of a part of the workpiece during execution of the method shown in FIG. 17. FIG. 18 is a cross-sectional view showing a state of a part of the workpiece during execution of the method shown in FIG. 17. It is sectional drawing which shows the state of a part of workpiece after execution of the method shown in FIG. 18 is a flowchart showing in detail some steps of the method shown in FIG. FIGS. 25A and 25B are flowcharts showing in detail some steps of 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.

  FIG. 1 is a flow diagram illustrating a method according to one embodiment. A method MT shown in FIG. 1 is a method of selectively etching a first region formed of silicon nitride with respect to a second region formed of silicon oxide. In one embodiment, the method MT selectively etches the first region relative to the second region and a third region formed from silicon. In the method MT, first, in step STP, a workpiece is prepared in a chamber provided by a chamber body of a plasma processing apparatus.

  FIG. 2 is an enlarged cross-sectional view of a part of an example workpiece to which the method according to the embodiment can be applied. The workpiece W shown in FIG. 2 has a first region R1 and a second region R2. The workpiece W may further include a third region R3. The first region R1 is made of silicon nitride, the second region R2 is made of silicon oxide, and the third region R3 is made of silicon. The third region R3 is made of, for example, polycrystalline silicon. In the workpiece W shown in FIG. 2, the first region R1, the second region R2, and the third region R3 are provided on the base layer UL. The layout in the workpiece W of the first region R1, the second region R2, and the third region R3 is not limited to the layout shown in FIG.

  FIG. 3 is an enlarged cross-sectional view illustrating a part of another example workpiece to which the method according to the embodiment can be applied. A workpiece W shown in FIG. 3 has a first region R1, a second region R2, and a third region R3, similarly to the workpiece W shown in FIG. The second region R2 is provided on both sides of the third region R3, and the third region R3 is provided so as to protrude from the second region R2. The first region R1 is provided so as to cover the second region R2 and the third region R3. 3 is an intermediate product obtained during the manufacture of the Fin-type field effect transistor, and the third region R3 is a fin region that provides a source region, a drain region, and a channel region. Used as

  FIG. 4 is a diagram schematically illustrating a plasma processing apparatus that can be used in methods according to various embodiments. A plasma processing apparatus 10 illustrated in FIG. 4 includes an ICP (Inductively Coupled Plasma) type plasma source. The plasma processing apparatus 10 includes a chamber body 12. The chamber body 12 is made of a metal such as aluminum. The chamber body 12 has, for example, a substantially cylindrical shape. The chamber body 12 provides its internal space as a chamber 12c. The chamber 12c is used as a space for plasma processing.

  A stage 14 is provided at the bottom of the chamber body 12. The stage 14 is configured to hold the workpiece W mounted thereon. The stage 14 can be supported by the support portion 13. The support portion 13 extends upward from the bottom of the chamber body 12 in the chamber 12c. The support part 13 may have a substantially cylindrical shape, for example. The support portion 13 can be formed of an insulating material such as quartz.

  The stage 14 has 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 made of a metal such as aluminum. The first plate 18a and the second plate 18b may have a substantially disk shape, for example. The second plate 18b is provided on the first plate 18a. The second plate 18b is electrically connected to the first plate 18a.

  The electrostatic chuck 16 is provided on the second plate 18b. The electrostatic chuck 16 has an insulating layer and a film-like electrode built in the insulating layer. A DC power supply 22 is electrically connected to the electrode of the electrostatic chuck 16 via a switch 23. The electrostatic chuck 16 generates an electrostatic force generated by a DC voltage from the DC power supply 22. The workpiece W is attracted to the electrostatic chuck 16 by electrostatic force and is held by the electrostatic chuck 16.

  When the plasma processing apparatus 10 is used, the focus ring FR is disposed on the peripheral edge of the second plate 18b so as to surround the edge of the workpiece W and the edge of the electrostatic chuck 16. The focus ring FR is used to improve the uniformity of plasma processing. The focus ring FR can be made of, for example, quartz.

  A flow path 24 is formed in the second plate 18b. A heat exchange medium, for example, a refrigerant is supplied to the flow path 24 from a temperature controller (for example, a chiller unit) provided outside the chamber body 12 for adjusting the temperature of the stage 14. The temperature regulator is a device that regulates the temperature of the heat exchange medium. A heat exchange medium is supplied to the flow path 24 from the temperature controller via the pipe 26a. The heat exchange medium supplied to the flow path 24 is returned to the temperature controller via the pipe 26b. By supplying the heat exchange medium whose temperature has been adjusted by the heat exchange controller to the flow path 24 of the stage 14, the temperature of the stage 14 and thus the temperature of the workpiece W are adjusted. In the plasma processing apparatus 10, the gas supply line 28 extends to the upper surface of the electrostatic chuck 16 through the stage 14. Between the upper surface of the electrostatic chuck 16 and the back surface of the workpiece W, a heat transfer gas from a heat transfer gas supply mechanism, for example, He gas, is supplied via a gas supply line 28. Thereby, heat exchange between the stage 14 and the workpiece W is promoted.

  A heater HT may be provided in the stage 14. The heater HT is a heating element. For example, the heater HT is embedded in the second plate 18 b or in the electrostatic chuck 16. The heater HT is connected to the heater power source HP. By supplying electric power from the heater power source HP to the heater HT, the temperature of the stage 14 is adjusted, and consequently the temperature of the workpiece W is adjusted.

  A high frequency power supply 30 is connected to the lower electrode 18 of the stage 14 via a matching unit 32. A high frequency from a high frequency power supply 30 can be supplied to the lower electrode 18. The high frequency power supply 30 generates a high frequency for drawing ions into the workpiece W mounted on the stage 14, that is, a high frequency for bias. The high frequency for bias has, for example, a frequency within a range of 400 [kHz] to 40.68 [MHz], and in one example, a frequency of 13.56 [MHz]. The matching unit 32 has a circuit for matching the output impedance of the high frequency power supply 30 with the impedance on the load side (lower electrode 18 side). In the plasma processing apparatus 10, plasma can be generated without using other high frequency for plasma generation by supplying a high frequency for bias to the lower electrode 18.

In the plasma processing apparatus 10, a shield 34 is detachably provided along the inner wall of the chamber body 12. The shield 34 is also provided on the outer periphery of the support portion 13. The shield 34 is a member for preventing etching by-products from adhering to the chamber body 12. The shield 34 can be configured by coating a ceramic such as Y ₂ O _{3 on} the surface of an aluminum base material.

An exhaust path is formed between the stage 14 and the side wall of the chamber body 12. This exhaust path is connected to an exhaust port 12 e formed at the bottom of the chamber body 12. An exhaust device 38 is connected to the exhaust port 12e via a pipe 36. The exhaust device 38 includes a pressure regulator and a vacuum pump such as a turbo molecular pump. A baffle plate 40 is provided in the exhaust path, that is, between the stage 14 and the side wall of the chamber body 12. The baffle plate 40 has a plurality of through holes penetrating the baffle plate 40 in the plate thickness direction. The baffle plate 40 can be configured, for example, by coating the surface of an aluminum base material with ceramics such as Y ₂ O ₃ .

  The top of the chamber body 12 is open. This opening is closed by a window member 42. The window member 42 is formed from a dielectric such as quartz. The window member 42 has a plate shape, for example.

  A gas inlet 12 i is formed on the side wall of the chamber body 12. A gas supply unit 44 is connected to the gas inlet 12 i via a pipe 46. The gas supply unit 44 supplies a first gas and a second gas described later to the chamber 12c. The gas supply unit 44 includes a gas source group 44a, a flow rate controller group 44b, and a valve group 44c. The gas source group 44a includes a plurality of gas sources. The plurality of gas sources includes a source of one or more gases included in the first gas and a source of one or more gases included in the second gas. The flow rate controller group 44b includes a plurality of flow rate controllers. Each of the plurality of flow controllers is a mass flow controller or a pressure-controlled flow controller. The valve group 44c includes a plurality of valves. A plurality of gas sources in the gas source group 44a are introduced through a corresponding flow rate controller among the plurality of flow rate controllers in the flow rate controller group 44b and a corresponding valve among the plurality of valves in the valve group 44c. It is connected to the mouth 12i. Note that the gas inlet 12 i may be formed not at the side wall of the chamber body 12 but at other locations such as the window member 42.

  An opening 12 p is formed in the side wall of the chamber body 12. The opening 12p is formed when the workpiece W is loaded into the chamber 12c from the outside of the chamber body 12 and when the workpiece W is unloaded from the chamber 12c to the outside of the chamber body 12. This is a passage through which W passes. A gate valve 48 for opening and closing the opening 12 p is attached to the side wall of the chamber body 12.

  An antenna 50 and a shield member 60 are provided on the top of the chamber body 12 and on the window member 42. The antenna 50 and the shield member 60 are provided outside the chamber body 12. In one embodiment, the antenna 50 includes an inner antenna element 52A and an outer antenna element 52B. The inner antenna element 52 </ b> A is a spiral coil and extends on the central portion of the window member 42. The outer antenna element 52B is a spiral coil, and extends on the window member 42 and outside the inner antenna element 52A. Each of the inner antenna element 52A and the outer antenna element 52B is formed of a conductor such as copper, aluminum, and stainless steel.

  Both the inner antenna element 52 </ b> A and the outer antenna element 52 </ b> B are sandwiched by a plurality of sandwiching bodies 54, and are supported by the plurality of sandwiching bodies 54. Each of the plurality of sandwiching bodies 54 has a bar shape. The plurality of sandwiching bodies 54 extend radially from the vicinity of the center of the inner antenna element 52A to the outer side of the outer antenna element 52B.

  The shield member 60 covers the antenna 50. The shield member 60 includes an inner shield wall 62A and an outer shield wall 62B. The inner shield wall 62A has a cylindrical shape. The inner shield wall 62A is provided between the inner antenna element 52A and the outer antenna element 52B so as to surround the inner antenna element 52A. The outer shield wall 62B has a cylindrical shape. The outer shield wall 62B is provided outside the outer antenna element 52B so as to surround the outer antenna element 52B.

  A disc-shaped inner shield plate 64A is provided on the inner antenna element 52A so as to close the opening of the inner shield wall 62A. An outer shield plate 64B having an annular plate shape is provided on the outer antenna element 52B so as to close the opening between the inner shield wall 62A and the outer shield wall 62B.

  In addition, the shape of the shield wall and the shield plate of the shield member 60 is not limited to the shape described above. The shape of the shield wall of the shield member 60 may be another shape such as a square tube shape.

  A high-frequency power source 70A and a high-frequency power source 70B are connected to the inner antenna element 52A and the outer antenna element 52B, respectively. The inner antenna element 52A and the outer antenna element 52B are respectively supplied with high frequencies having the same frequency or different frequencies from the high frequency power source 70A and the high frequency power source 70B. When a high frequency from the high frequency power supply 70A is supplied to the inner antenna element 52A, an induction magnetic field is generated in the chamber 12c, and the gas in the chamber 12c is excited by the induction magnetic field. Thereby, plasma is generated above the central region of the workpiece W. When a high frequency from the high frequency power supply 70B is supplied to the outer antenna element 52B, an induced magnetic field is generated in the chamber 12c, and the gas in the chamber 12c is excited by the induced magnetic field. Thereby, an annular plasma is generated above the peripheral region of the workpiece W.

  Note that the electrical lengths of the inner antenna element 52A and the outer antenna element 52B need to be adjusted in accordance with the high frequency output from each of the high frequency power supply 70A and the high frequency power supply 70B. For this reason, the positions in the height direction of the inner shield plate 64A and the outer shield plate 64B are individually adjusted by the actuator 68A and the actuator 68B.

  The plasma processing apparatus 10 may further include a control unit 80. The control unit 80 can be a computer including a storage unit such as a processor and a memory, an input device, a display device, and the like. The control unit 80 operates according to the control program and recipe data stored in the storage unit, and can control various elements of the plasma processing apparatus 10. Specifically, the control unit 80 includes a plurality of flow controllers in the flow controller group 44b, a plurality of valves in the valve group 44c, an exhaust device 38, a high frequency power supply 70A, a high frequency power supply 70B, a high frequency power supply 30, a matching unit 32, and a heater. Various elements of the plasma processing apparatus such as the power source HP are controlled. Note that the controller 80 can also control various elements of the plasma processing apparatus 10 in accordance with the control program and recipe data when executing the methods according to various embodiments.

  Hereinafter, the method MT will be described in detail with reference to FIG. 1 again. In the following description, (a) in FIG. 5, (b) in FIG. 5, (a) in FIG. 6, (b) in FIG. 6, (c) in FIG. 6, (a) in FIG. 7 (b) and FIG. 7 (c) are referred to. FIG. 5A is a diagram for explaining a process ST1 of the method according to the embodiment, and FIG. 5B is a state of the workpiece after execution of the process ST1 of the method according to the embodiment. FIG. 6A is a diagram for explaining a process ST2 of the method according to the embodiment, and FIG. 6B is a state of the workpiece after the process ST2 of the method according to the embodiment is performed. FIG. 6C is a diagram illustrating a state of the workpiece at the end of the method according to the embodiment. FIG. 7A is a diagram illustrating a state of the workpiece after execution of step ST1 of the method according to the embodiment, and FIG. 7B is after execution of step ST2 of the method according to the embodiment. FIG. 7C is a diagram showing the state of the workpiece at the end of the method according to the embodiment.

  As shown in FIG. 1, in step STP of the method MT, the workpiece W shown in FIG. 2 or FIG. 3 is prepared in a chamber provided by the chamber body of the plasma processing apparatus. The workpiece W is placed on a stage having a lower electrode. When the plasma processing apparatus 10 is used, the workpiece W is placed on the stage 14 and held by the electrostatic chuck 16.

In the method MT, the process ST1 and the process ST2 are sequentially performed in a state where the workpiece W is placed on the stage 14. In step ST1, a first gas plasma PL1 is generated in the chamber. The first gas includes a gas containing hydrogen. The gas containing hydrogen can be, for example, H ₂ gas and / or NH ₃ gas.

  In step ST1, as shown in FIG. 5A, the surface of the workpiece W is irradiated with active species of hydrogen, for example, hydrogen ions, from the plasma PL1. In FIG. 5A, a circular figure surrounding the letter “H” represents an active species of hydrogen. When the surface of the workpiece W is irradiated with the active species of hydrogen, as shown in FIG. 5B, a part of the first region R1, that is, a part of the first region R1 including the surface is modified. Thus, the modified region MR1 is obtained. In the case of the workpiece W of FIG. 3, the modified region MR1 is formed as shown in FIG. The modified region MR1 can be easily removed by the active species of fluorine. On the other hand, the second region R2 is stable and is not reformed by the active species of hydrogen.

  In step ST1 of one embodiment, a high frequency for bias is supplied to the lower electrode of the stage. In the process ST1 of one embodiment, plasma may be generated only by the high frequency for bias. When a high frequency for bias is supplied to the lower electrode, hydrogen ions are strongly drawn into the workpiece W and the modification of the first region R1 is promoted, and the modified region MR1 in the film thickness direction of the first region R1. The thickness of increases. Note that the high-frequency bias power supplied to the lower electrode in step ST1 is set so that etching by sputtering does not occur.

When the workpiece W has the third region R3, the first gas may further include a gas containing oxygen. The gas containing oxygen is, for example, any one of O ₂ gas, CO gas, CO ₂ gas, NO gas, NO ₂ gas, N ₂ O gas, SO ₂ gas, or two or more of these gases It may be a mixed gas containing. When the first gas contains oxygen-containing gas, the surface of the workpiece W is irradiated with active species of oxygen, for example, oxygen ions, as shown in FIG. In FIG. 5A, a circular figure surrounding the letter “O” represents an active species of oxygen. When the surface of the workpiece W is irradiated with the active species of oxygen, as shown in FIG. 5B, a part of the third region R3, that is, a part of the third region R3 including the surface is oxidized. Thus, the oxidized region MR3 is obtained. When the surface of the third region R3 is oxidized in this way, the etching of the third region R3 is suppressed in the process ST2 described later.

  In one embodiment, the ratio of the flow rate of the gas containing oxygen in the first gas to the flow rate of the gas containing hydrogen in the first gas may be 3/100 or more and 9/100 or less. Thus, by setting the ratio of the flow rate of the gas containing oxygen in the first gas to the flow rate of the gas containing hydrogen in the first gas, the first region including the oxidation region MR3 in step ST2 to be described later. Etching of the three regions R3 is further suppressed. Moreover, the fall of the etching rate of 1st area | region R1 in below-mentioned process ST2 is suppressed.

  When the plasma processing apparatus 10 is used, in step ST1, a first gas containing a gas containing hydrogen is supplied from the gas supply unit 44 to the chamber 12c. The first gas supplied to the chamber 12c may include a gas containing oxygen. The flow rates of one or more gases included in the first gas are each controlled by a corresponding flow rate controller of the flow rate controller group 44b. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Moreover, a high frequency for bias from the high frequency power supply 30 may be supplied to the lower electrode 18. In step ST1, high-frequency power may be supplied from the high-frequency power source 70A and the high-frequency power source 70B to the inner antenna element 52A and the outer antenna element 52B, respectively, in order to generate plasma. That is, in step ST1, by supplying a high frequency for bias to the lower electrode 18, plasma may be generated without using another high frequency.

In the subsequent step ST2, the plasma PL2 of the second gas is generated in the chamber. The second gas includes a gas containing fluorine. The gas containing fluorine can be any gas containing fluorine. For example, the gas containing fluorine may be any one of NF ₃ gas, SF ₆ gas, and fluorocarbon gas (for example, CF ₄ gas), or a mixed gas including two or more of these gases. In addition to the gas containing fluorine, the second gas may include other gases, for example, a rare gas such as O ₂ gas and Ar gas.

  In step ST2, as shown in FIG. 6A, the surface of the workpiece W is irradiated with active species of fluorine from the plasma PL2. In FIG. 6A, a circular figure surrounding the letter “F” represents an active species of fluorine. When the surface of the workpiece W is irradiated with the active species of fluorine, as shown in FIG. 6B, the modified region MR1 is selectively etched and removed by the active species of fluorine. In the case of the workpiece W in FIG. 3, the modified region MR1 is removed as shown in FIG. 7B.

  In the process ST2 of one embodiment, the high frequency for bias is not supplied to the lower electrode of the stage. When the bias high frequency is not supplied to the lower electrode in step ST2, etching is performed mainly by fluorine radicals instead of fluorine ions as the active species of fluorine. In other words, radical etching is performed instead of sputter etching using ions. Thereby, the etching of the third region R3 including the second region R2 and the oxidized region MR3 is suppressed. Further, the modified region MR1 is removed by a chemical reaction between the modified region MR1 and the active species of fluorine.

In step ST2 of one embodiment, the second gas may contain hydrogen. When the second gas contains hydrogen, the ratio of the number of hydrogen atoms in the second gas to the number of fluorine atoms in the second gas is 8/9 or more. In the second gas, when the fluorine-containing gas is NF ₃ gas and the hydrogen-containing gas is H ₂ gas, the _second gas with respect to the flow rate of the NF ₃ gas in the second gas The ratio of the flow rate of H ₂ gas in the gas is 3/4 or more. The ratio of the number of hydrogen atoms in the second gas to the number of fluorine atoms in the second gas, or the flow rate of H ₂ gas in the _second gas relative to the flow rate of NF ₃ gas in the _second gas. When the ratio is set as described above, silicon nitride, silicon oxide, and silicon are hardly etched. However, the silicon nitride modified by hydrogen is etched. That is, the modified region MR1 is etched. Accordingly, the etching selectivity of the first region R1 is further improved.

  When the plasma processing apparatus 10 is used, in step ST2, a second gas containing a fluorine-containing gas is supplied from the gas supply unit 44 to the chamber 12c. The second gas supplied to the chamber 12c may include a gas containing hydrogen. The flow rates of one or more gases included in the second gas are each controlled by a corresponding flow rate controller of the flow rate controller group 44b. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Further, a high frequency from the high frequency power supply 70A is supplied to the inner antenna element 52A, and a high frequency from the high frequency power supply 70B is supplied to the outer antenna element 52B. The high frequency for bias from the high frequency power supply 30 is not supplied to the lower electrode 18 or its power is relatively small.

  As shown in FIG. 1, in the subsequent step STJ, it is determined whether or not a stop condition is satisfied. The stop condition is determined to be satisfied when the number of executions of the sequence including the process ST1 and the process ST2 reaches a predetermined number. If it is determined in step STJ that the stop condition is not satisfied, step ST1 is executed again. On the other hand, if it is determined that the stop condition is satisfied, the method MT ends. At the end of the method MT, as shown in FIG. 6C, the first region R1 is removed from the workpiece W shown in FIG. Alternatively, as shown in FIG. 7C, the first region R1 is removed from the workpiece W shown in FIG.

  In the method MT, a part of the first region R1 is modified by the active species of hydrogen generated in the step ST1, so that the modified region MR1 can be easily removed by the active species of fluorine. On the other hand, since the second region R2 formed of silicon oxide is stable, it is not modified by the active species of hydrogen. Therefore, in step ST2, the modified region MR1 is selectively removed with respect to the second region R2. Therefore, according to the method MT, the first region R1 is selectively etched with respect to the second region R2. In addition, the active species in the plasma generated in the steps ST1 and ST2 have a considerably low deposition property or substantially a deposition property compared to the active species in the plasma of the hydrofluorocarbon gas. Not done. Therefore, according to the method MT, the generation of deposits is suppressed.

  Further, when the workpiece W has the third region R3, as described above, the gas containing oxygen is included in the first gas. Thereby, in the process ST1, the surface of the third region R3 is oxidized by the active species of oxygen, and the etching of the third region R3 including the oxidized region MR3 is suppressed in the etching of the process ST2. Accordingly, the first region R1 is selectively etched with respect to the second region R2 and the third region R3.

  Further, as described above, in one embodiment, the ratio of the flow rate of the gas containing oxygen in the first gas to the flow rate of the gas containing hydrogen in the first gas is 3/100 or more, 9 / Set to 100 or less. In this embodiment, the etching of the third region R3 including the oxidized region MR3 is further suppressed in step ST2. In addition, a decrease in the etching rate of the first region R1 in the process ST2 is suppressed. As a result, the first region R1 can be etched with a higher selectivity than the third region R3.

  Hereinafter, a method according to another embodiment will be described. FIG. 8 is a flowchart illustrating a method according to another embodiment. The method MTA shown in FIG. 8 can be applied to a workpiece in which the second region R2 and the third region R3 are covered by the first region R1, such as the workpiece W shown in FIG.

  The method MTA includes the same step STP as the step STP of the method MT. The method MTA further includes a plurality of sequences SQ that are executed in sequence. Each of the plurality of sequences SQ includes a process ST1 similar to the process ST1 of the method MT and a process ST2 similar to the process ST2 of the method MT.

  The plurality of sequences SQ include one or more first sequences SQ1 and one or more second sequences SQ2. The one or more first sequences SQ1 are one or more sequences including a sequence executed first among a plurality of sequences. The one or more second sequences SQ2 are sequences that are executed after the one or more first sequences SQ1 among the plurality of sequences SQ. One or more second sequences SQ2 are sequences including a process ST1 for oxidizing the surface of the third region R3.

  The method MTA includes steps STJ1 and STJ2. In step STJ1, it is determined whether or not a stop condition is satisfied. In step STJ1, it is determined that the stop condition is satisfied when the number of executions of the first sequence SQ1 has reached a predetermined number. If it is determined in step STJ1 that the stop condition is not satisfied, the first sequence SQ1 is executed again. On the other hand, if it is determined in step STJ1 that the stop condition is satisfied, the process proceeds to the execution of the second sequence SQ2.

  In step STJ2, it is determined whether or not a stop condition is satisfied. In step STJ2, it is determined that the stop condition is satisfied when the number of executions of the second sequence SQ2 has reached a predetermined number. If it is determined in step STJ2 that the stop condition is not satisfied, the second sequence SQ2 is executed again. On the other hand, when it is determined in step STJ2 that the stop condition is satisfied, the execution of the method MTA ends.

  FIGS. 9A and 9B are diagrams for explaining the process ST1 in the first sequence and the process ST1 in the second sequence in the first example of the method shown in FIG. FIG. 9C is a diagram illustrating a state in which the surface of the third region is oxidized by the execution of the process ST1 in the second sequence. In the first example of the method MTA, one or more first sequences SQ1 are executed until the third region R3 is exposed. In the first example of the method MTA, the first gas used in the step ST1 of the one or more first sequences SQ1 does not include a gas containing oxygen. Accordingly, as shown in FIG. 9A, in the step ST1 of one or more first sequences SQ1, the workpiece W is not irradiated with the active species of oxygen, and the workpiece W is irradiated with the active species of hydrogen. Is done.

  In the first example of the method MTA, one or more second sequences SQ2 are executed immediately after the third region R3 is exposed. In step ST1 of one or more second sequences SQ2, the first gas contains a gas containing oxygen in addition to a gas containing hydrogen. Therefore, in the first example of the method MTA, as shown in FIG. 9B, immediately after the third region R3 is exposed, the workpiece W is irradiated with active species of hydrogen and active species of oxygen in step ST1. The As a result, as shown in FIG. 9C, immediately after the surface of the third region R3 is exposed, the surface of the third region R3 is oxidized to form an oxidized region MR3. Therefore, the third region R3 is protected from the etching of the fluorine active species in the step ST2. According to the first example of the method MTA, the first region R1 is selectively etched with respect to the second region R2 and the third region R3.

  FIG. 10A and FIG. 10B are diagrams for explaining the process ST1 in the first sequence and the process ST1 in the second sequence in the second example of the method shown in FIG. FIG. 10C is a diagram illustrating a state in which the surface of the third region is oxidized by the execution of the process ST1 in the second sequence. In the second example of the method MTA, one or more first sequences SQ1 are executed until just before the third region R3 is exposed. That is, one or more first sequences SQ1 are executed until a state in which the first region R1 is slightly left so as to cover the third region R3 is formed. In the second example of the method MTA, the first gas used in the step ST1 of the one or more first sequences SQ1 does not include a gas containing oxygen. Therefore, as shown in FIG. 10A, in the step ST1 of one or more first sequences SQ1, the workpiece W is not irradiated with the active species of oxygen, and the workpiece W is irradiated with the active species of hydrogen. Is done.

  In the one or more second sequences SQ2 in the second example of the method MTA, the first gas includes a gas containing oxygen in addition to a gas containing hydrogen. Therefore, in the second example of the method MTA, the workpiece W is irradiated with the active species of oxygen as shown in FIG. 10B after the time immediately before the third region R3 is exposed. Therefore, as shown in FIG. 10C, immediately after the surface of the third region R3 is exposed, the surface of the third region R3 is oxidized. Therefore, after the time immediately after the surface of the third region R3 is exposed, the third region R3 is protected from the etching of the fluorine active species in the step ST2. According to the second example of the method MTA, the first region R1 is selectively etched with respect to the second region R2 and the third region R3.

  Hereinafter, a method according to still another embodiment will be described. FIG. 11 is a flowchart illustrating a method according to still another embodiment. The method MTB shown in FIG. 11 is similar to the method MTA on a workpiece in which the second region R2 and the third region R3 are covered by the first region R1, such as the workpiece W shown in FIG. And can be applied. The method MTB further includes one or more third sequences SQ3 and step STJ3 in addition to step STP, one or more first sequences SQ1, step STJ1, one or more second sequences SQ2, and step STJ2. Yes.

  In the method MTB, the one or more second sequences SQ2 are ended after the surface of the third region R3 is oxidized. In the method MTB, when it is determined in step STJ2 that the stop condition is satisfied, the process proceeds to the execution of the third sequence SQ3. In step STJ3, it is determined whether or not a stop condition is satisfied. The stop condition is determined to be satisfied when the number of executions of the third sequence SQ3 reaches a predetermined number. If it is determined in step STJ3 that the stop condition is not satisfied, the third sequence SQ3 is executed again. On the other hand, when it is determined in step STJ3 that the stop condition is satisfied, the execution of the method MTB ends.

  12 (a), FIG. 12 (b), and FIG. 12 (c) are respectively the first sequence step ST1, the second sequence step ST1, and the third sequence step in the method shown in FIG. It is a figure for demonstrating ST1. In the method MTB, one or more first sequences SQ1 are executed until immediately before the third region R3 is exposed or until the third region R3 is exposed. In the step ST1 of the one or more first sequences SQ1, the first gas does not include a gas containing oxygen. Therefore, as shown in FIG. 12A, in the step ST1 of one or more first sequences SQ1, the workpiece W is not irradiated with the active species of oxygen, and the workpiece W is irradiated with the active species of hydrogen. Is done. In the step ST1 of the one or more first sequences SQ1, the first gas may include a gas containing oxygen.

  In the method MTB, one or more second sequences SQ2 are performed to oxidize the surface of the third region R3 after the one or more first sequences SQ1. In step ST1 of one or more second sequences SQ2, the first gas contains a gas containing oxygen in addition to a gas containing hydrogen. Therefore, according to one or more second sequences SQ2 of the method MTB, as shown in FIG. 12B, the workpiece W is irradiated with the active species of oxygen immediately after the third region R3 is exposed. In the method MTB, the one or more second sequences SQ2 are finished after the surface of the third region R3 is oxidized.

  In the method MTB, one or more third sequences SQ3 are executed after one or more second sequences SQ2. In step ST1 of one or more third sequences SQ3, the first gas does not include a gas containing oxygen. Accordingly, as shown in FIG. 12C, in the step ST1 of one or more third sequences SQ3, the workpiece W is not irradiated with the active species of oxygen, and the workpiece W is irradiated with the active species of hydrogen. Is done. In the method MTB, since the surface of the third region R3 is oxidized immediately after the exposure in one or more second sequences SQ2, a gas containing oxygen is contained in the first gas in step ST1 of the one or more third sequences SQ3. Even if it is not included, the third region R3 is protected from the etching of the fluorine active species in the step ST2. According to this method MTB, the first region R1 is selectively etched with respect to the second region R2 and the third region R3.

  Hereinafter, the results of various experiments will be described, but the present disclosure is not limited to these experiments.

  (First experiment)

The first experiment is an experiment conducted to derive a condition in which silicon nitride is not etched by the active species from the plasma of the second gas unless the silicon nitride is modified by the active species of hydrogen. In the first experiment, the silicon nitride film, the silicon oxide film, and the silicon film were processed with the plasma of the second gas in the chamber of the plasma processing apparatus 10. The second gas used in the first experiment was a gas containing NF ₃ gas, H ₂ gas, O ₂ gas, and Ar gas. In the first experiment, the flow rate of H ₂ gas in the _second gas was set to various flow rates. Hereinafter, other parameters in the first experiment are shown.

<Parameters of the first experiment>
-Pressure in chamber 12c: 400 [mTorr] (53.33 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 27 [MHz], 600 [W]
・ High frequency for bias: 0 [W]
-Flow rate of NF ₃ gas: 45 [sccm]
・ Flow rate of O ₂ gas: 300 [sccm]
Ar gas flow rate: 100 [sccm]
・ Processing time: 10 [seconds]

In the first experiment, the amount of reduction (length) of the film thickness of each of the silicon nitride film, the silicon oxide film, and the silicon film by the treatment using the plasma of the second gas, that is, the etching amount was measured. FIG. 13 (a), FIG. 13 (b), and FIG. 13 (c) show graphs representing the results of the first experiment. In each of the graphs of FIG. 13A, FIG. 13B, and FIG. 13C, the horizontal axis indicates the flow rate of H ₂ gas in the _second gas. The vertical axis of the graph of FIG. 13A indicates the etching amount of the silicon nitride film, the vertical axis of the graph of FIG. 13B indicates the etching amount of the silicon oxide film, and FIG. The vertical axis of the graph (c) indicates the etching amount of the silicon film.

As can be seen from FIGS. 13A, 13B, and 13C, when the flow rate of the H ₂ gas in the _second gas is 60 sccm or more, the silicon nitride film, The silicon oxide film and the silicon film were not substantially etched by the treatment using the plasma of the second gas. Therefore, in the treatment using the plasma of the second gas in which the ratio of the flow rate of the H ₂ gas in the _second gas to the flow rate of the NF ₃ gas in the _second gas is 3/4 or more, silicon nitride, oxidation It was confirmed that silicon and silicon were not etched. Therefore, when the ratio of the number of hydrogen atoms in the second gas to the number of fluorine atoms in the second gas is 8/9 or more, nitriding is performed in the treatment using the plasma of the second gas. It was confirmed that silicon, silicon oxide, and silicon were not etched.

  (Second experiment)

In the second experiment, the plasma processing apparatus 10 is used to apply the method MT to a silicon nitride film, a silicon oxide film, and a silicon film, and in the first gas with respect to the flow rate of H ₂ gas in the first gas. The relationship between the ratio of the flow rate of O ₂ gas and the etching selectivity of the silicon nitride film to the silicon oxide film and the silicon film was obtained. In the second experiment, the number of executions of the sequence including the steps ST1 and ST2 was six. Other parameters of the second experiment are shown below.

<Parameters of step ST1 in the second experiment>
-Pressure in chamber 12c: 30 [mTorr] (4 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 0 [W]
・ High frequency for bias: 13.56 [MHz], 50 [W]
・ H ₂ gas flow rate: 100 [sccm]
・ Processing time: 15 [seconds]
<Parameters of step ST2 in the second experiment>
-Pressure in chamber 12c: 400 [mTorr] (53.33 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 27 [MHz], 600 [W]
・ High frequency for bias: 0 [W]
-Flow rate of NF ₃ gas: 45 [sccm]
・ Flow rate of H ₂ gas: 60 [sccm]
・ Flow rate of O ₂ gas: 300 [sccm]
Ar gas flow rate: 100 [sccm]
・ Processing time: 10 [seconds]

In the second experiment, the reduction amount (length) of the silicon nitride film, the silicon oxide film, and the silicon film, that is, the etching amount was measured. Further, from the etching amount of the silicon nitride film and the etching amount of the silicon film, the ratio of the etching amount of the silicon nitride film to the etching amount of the silicon film, that is, the selection ratio of the etching of the silicon nitride film to the silicon film was obtained. The results are shown in FIG. 14 (a), FIG. 14 (b), and FIG. In each graph of FIG. 14A, FIG. 14B, and FIG. 15, the horizontal axis indicates the ratio of the flow rate of O ₂ gas to the flow rate of H ₂ gas. In the graph of FIG. 14A, the vertical axis indicates the etching amount of the silicon nitride film. In the graph of FIG. 14B, the vertical axis indicates the etching amount of the silicon oxide film and the etching amount of the silicon film. In the graph of FIG. 15, the vertical axis indicates the etching selectivity of the silicon nitride film to the silicon film.

As can be seen from the graph of FIG. 14 (b), the ratio of the flow rate of O ₂ gas in the first gas to the flow rate of H ₂ gas in the first gas is 3/100 or more (the ratio is 3% or more). In this case, it was confirmed that the etching amount of the silicon film decreases, that is, the etching of the silicon film is suppressed. Further, as can be seen from the graph of FIG. 14A, the ratio of the flow rate of O ₂ gas in the first gas to the flow rate of H ₂ gas in the first gas is 9/100 or less (9% in the ratio). The etching amount of the silicon nitride film is the silicon nitride film when the ratio of the flow rate of O ₂ gas in the first gas to the flow rate of H ₂ gas in the first gas is 0 It was almost equal to the etching amount. That is, when the ratio of the flow rate of O ₂ gas in the first gas to the flow rate of H ₂ gas in the first gas is 9/100 or less, the etching amount of the silicon nitride film was not substantially reduced. Therefore, as shown in FIG. 15, if the ratio of the flow rate of O ₂ gas in the first gas to the flow rate of H ₂ gas in the first gas is 3/100 or more and 9/100 or less, the silicon film It has been confirmed that the etching selectivity of the silicon nitride film with respect to the film is high.

  (Third experiment)

In the third experiment, the method MT was applied to the experimental sample 1 and the experimental sample 2 similar to the workpiece W illustrated in FIG. 3 using the plasma processing apparatus 10. In the method MT applied to the experimental sample 1, O ₂ gas was not included in the first gas. In the method MT applied to the experimental sample 2, O ₂ gas was included in the first gas. Further, a plasma treatment of a treatment gas containing a hydrofluorocarbon gas was performed on the comparative sample similar to the workpiece W shown in FIG. Hereinafter, parameters of the method MT applied to the experimental sample 1, parameters of the method MT applied to the experimental sample 2, and parameters of plasma processing applied to the comparative sample are shown. In the method MT applied to the experimental sample 1 and the method MT applied to the experimental sample 2, the process is performed until the first region R1 is completely removed, and the sequence including the steps ST1 and ST2 is performed. The number of executions was 33 times. Similarly, in the plasma processing for the comparative sample, the processing was performed until the first region R1 was completely removed.

<Parameter of Step ST1 of Method MT for Experimental Sample 1 in Third Experiment>
-Pressure in chamber 12c: 30 [mTorr] (4 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 0 [W]
・ High frequency for bias: 13.56 [MHz], 50 [W]
・ H ₂ gas flow rate: 100 [sccm]
・ Flow rate of O ₂ gas: 0 [sccm]
・ Processing time: 15 [seconds]
<Parameter of Step ST2 of Method MT for Experimental Sample 1 in Third Experiment>
-Pressure in chamber 12c: 400 [mTorr] (53.33 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 27 [MHz], 600 [W]
・ High frequency for bias: 0 [W]
-Flow rate of NF ₃ gas: 45 [sccm]
・ Flow rate of H ₂ gas: 60 [sccm]
・ Flow rate of O ₂ gas: 300 [sccm]
Ar gas flow rate: 100 [sccm]
・ Processing time: 10 [seconds]

<Parameter of Step ST1 of Method MT for Experimental Sample 2 in Third Experiment>
-Pressure in chamber 12c: 30 [mTorr] (4 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 0 [W]
・ High frequency for bias: 13.56 [MHz], 50 [W]
・ H ₂ gas flow rate: 100 [sccm]
・ Flow rate of O ₂ gas: 9 [sccm]
・ Processing time: 15 [seconds]
<Parameter of Step ST2 of Method MT for Experimental Sample 2 in Third Experiment>
-Pressure in chamber 12c: 400 [mTorr] (53.33 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 27 [MHz], 600 [W]
・ High frequency for bias: 0 [W]
-Flow rate of NF ₃ gas: 45 [sccm]
・ Flow rate of H ₂ gas: 60 [sccm]
・ Flow rate of O ₂ gas: 300 [sccm]
Ar gas flow rate: 100 [sccm]
・ Processing time: 10 [seconds]

<Parameters of plasma treatment applied to comparative sample>
-Pressure in chamber 12c: 50 [mTorr] (6.666 [Pa])
-High frequency of the high frequency power supplies 70A and 70B: 27 [MHz], 200 [W]
・ High frequency for bias: 50 [W]
-CH ₃ F gas flow rate: 30 [sccm]
・ Flow rate of O ₂ gas: 15 [sccm]
・ He gas flow rate: 500 [sccm]

  (A) of FIG. 16 is a figure for demonstrating the reduction | decrease amount calculated | required about each sample in 3rd experiment. In FIG. 16A, the second region R2 and the third region R3 before the processing of each sample are indicated by a two-dot chain line, and the second region R2 and the third region after the processing of each sample are indicated by a solid line. R3 is shown. In the third experiment, as shown in FIG. 16A, the reduction amount ΔL2 of the second region R2 and the reduction amount ΔL3 of the third region R3 were obtained for each sample. The results are shown in the table of FIG. As can be seen from the result of the comparative sample shown in the table of FIG. 16B, in the plasma treatment using the treatment gas containing the hydrofluorocarbon gas, not only the first region R1 is etched but also the second region R2 and The third region R3 was also etched. On the other hand, as can be seen from the result of the experimental sample 1 shown in the table of FIG. 16B, in the method MT, the second region R2 is obtained by reforming using the plasma of the first gas including the gas containing hydrogen. It was confirmed that the first region R1 can be selectively etched without etching. However, in the method MT applied to the experimental sample 1, the third region R3 was etched because the first gas did not contain oxygen-containing gas. In the case of the experimental sample 2 to which the method MT using the first gas including the gas containing oxygen is applied, the first region R1 is selected without etching both the second region R2 and the third region R3. It was confirmed that it was possible to perform etching.

  Hereinafter, a method according to still another embodiment will be described. FIG. 17 is a flowchart illustrating a method according to still another embodiment. In the following description, FIGS. 18 to 25 are referred to together with FIG. In the method MTC shown in FIG. 17, after the second region is formed on the workpiece having the first region, the sequence including the above-described steps ST1 and ST2 is executed once or more. Hereinafter, although the method MTC performed using the plasma processing apparatus 10 will be described, the method MTC may be performed using a plasma processing apparatus other than the plasma processing apparatus 10.

  In step STP of method MTC, workpiece W shown in FIG. 18 is placed on stage 14 of plasma processing apparatus 10. A workpiece W shown in FIG. 18 has a base layer UL and a region EL. The region EL is provided on the base layer UL. The surface of the foundation layer UL includes a main surface UL1. The main surface UL1 is a surface perpendicular to the direction DR. The direction DR corresponds to the vertical direction when the workpiece W is placed on the stage 14 (on the electrostatic chuck 16).

  The region EL includes a plurality of convex regions (for example, the convex region PJ1, the convex region PJ2, etc.). Each of the plurality of convex regions of the region EL extends upward from the main surface UL11. Each of the plurality of convex regions of the region EL has an end face. The convex region PJ1 has an end face TE1. The convex region PJ2 has an end face TE2. In the workpiece W shown in FIG. 18, the end surfaces of the plurality of convex regions of the region EL are exposed. The end surface TE1 of the convex region PJ1 and the end surface TE2 of the convex region PJ2 are exposed.

  The height of each of the plurality of convex regions is the distance between the end surface and the main surface UL1. The height TT1 of the convex region PJ1 is a distance between the end surface TE1 and the main surface UL1. The height TT2 of the convex region PJ2 is a distance between the end surface TE2 and the main surface UL1. The heights of the plurality of convex regions in the region EL are different from each other. The convex region PJ1 is lower than the convex region PJ2. That is, the value of the height TT1 of the convex region PJ1 is smaller than the value of the height TT2 of the convex region PJ2.

  The underlayer UL is made of, for example, Si (silicon). The region EL is made of, for example, silicon nitride. That is, the entire region EL may be the first region formed from silicon nitride. Or the some convex area | region may be formed from a mutually different material. For example, some of the plurality of convex regions may be formed of a material different from the material of the other convex regions. For example, the convex region PJ1 may be formed from silicon nitride, and the other convex region may be formed from one or more other materials such as silicon. In this case, the convex region PJ1 is a first region formed from silicon nitride.

  End portions (portions including end surfaces such as end surface TE1 and end surface TE2) of the plurality of convex regions (convex region PJ1, convex region PJ2, etc.) of region EL have their widths depending on the distance from main surface UL1. May be formed to be narrow. That is, the ends of the plurality of convex regions in the region EL may have a tapered shape. When the ends of the plurality of convex regions in the region EL have a tapered shape, the width of the opening defined by the ends of the plurality of convex regions becomes relatively wide. The formation of deposits in can be sufficiently suppressed.

  As shown in FIG. 17, the process STP includes a process ST11 and a process ST12. In step ST11, the first film SF1 is conformally formed on the surface of the workpiece W in a state where the workpiece W shown in FIG. 18 is placed on the stage. The first film SF1 is formed from silicon oxide. The film forming method in step ST11 is an ALD (Atomic Layer Deposition) method. FIG. 24 shows a detailed flowchart of step ST11. As shown in FIG. 24, the process ST11 includes a process ST11a, a process ST11b, a process ST11b, and a process ST11d. Step ST11a, step ST11b, step ST11b, and step ST11d constitute a sequence SQ11. In step ST11, the sequence SQ11 is executed once or more.

In step ST11a, the third gas is supplied from the gas supply unit 44 to the chamber 12c in which the workpiece W is accommodated. The third gas includes an aminosilane-based gas, for example, an organic-containing aminosilane-based gas. As the organic-containing aminosilane-based gas, for example, monoaminosilane (H ₃ —Si—R (R is an organic-containing amino group)) is used. In step ST11a, the plasma of the third gas is not generated. In step ST11a, molecules (for example, monoaminosilane) in the third gas adhere to the surface of the workpiece W as a precursor. The aminosilane-based gas contained in the third gas may contain aminosilane having 1 to 3 silicon atoms in addition to monoaminosilane. Further, the aminosilane-based gas contained in the third gas may contain aminosilane having 1 to 3 amino groups.

  In the subsequent process ST11b, the chamber 12c is purged. That is, in step ST11b, the third gas is exhausted. In step ST11b, an inert gas such as a nitrogen gas or a rare gas may be supplied to the chamber 12c as the purge gas. In the process ST11b, molecules excessively attached on the workpiece W can be removed. By performing step ST11b, the precursor layer on the workpiece W becomes a very thin layer (for example, a monomolecular layer).

  In step ST11c, plasma of the fourth gas is generated in the chamber 12c. The fourth gas includes a gas containing oxygen atoms. The fourth gas can include, for example, oxygen gas. In step ST11c, the fourth gas is supplied from the gas supply unit 44 to the chamber 12c. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Further, high frequency power is supplied from the high frequency power supply 70A and the high frequency power supply 70B to the inner antenna element 52A and the outer antenna element 52B, respectively. A high frequency for bias from the high frequency power supply 30 may be supplied to the lower electrode 18. In step ST11c, the fourth gas is excited and plasma is generated. The precursor layer is then exposed to oxygen active species from the plasma. As a result, the precursor layer becomes a silicon oxide film (first film SF1 or a part thereof).

  In the subsequent step ST11d, the chamber 12c is purged. That is, in step ST11d, the fourth gas is exhausted. In step ST11d, an inert gas such as nitrogen gas or a rare gas may be supplied to the chamber 12c as the purge gas.

  In the subsequent step ST11e, it is determined whether or not to end the execution of the sequence SQ11. Specifically, in step ST11e, it is determined whether or not the number of executions of the sequence SQ11 has reached a preset number. If it is determined in step ST11e that the number of executions of the sequence SQ11 has not reached the preset number, the sequence SQ11 is executed again. On the other hand, when it is determined in step ST11e that the number of executions of the sequence SQ11 has reached a preset number, the execution of the step ST11 is ended. By performing this step ST11, as shown in FIG. 19, the first film SF1 is conformally formed on the surface of the workpiece W. The film thickness of the first film SF1 is defined by the number of executions of the sequence SQ11. That is, the film thickness of the first film SF1 is represented by the product of the film thickness of the silicon oxide film formed by one execution of the sequence SQ11 and the number of executions of the sequence SQ11. The number of executions of the sequence SQ11 is set according to a desired film thickness of the first film SF1.

  Returning to FIG. 17, in the method MTC, the process ST12 is then executed. In step ST12, the second film SF2 is formed on the first film SF1. The second film SF2 is formed from silicon oxide. In step ST12, the second film SF2 is formed such that the film thickness increases as the distance from the main surface UL1 at the formation position increases. For example, as shown in FIG. 20, the first film on the end surface TE2 of the convex region PJ2 is larger than the film thickness of the second film SF2 formed on the first film SF1 on the end surface TE1 of the convex region PJ1. The film thickness of the second film SF2 formed on SF1 is large.

  For the film formation process in step ST12, step ST12A shown in FIG. 25A or step ST12B shown in FIG. 25B can be used. Hereinafter, step ST12A and step ST12B will be described.

Step ST12A includes step ST121 and step ST122. In step ST121, plasma of the fifth gas is generated in the chamber 12c. The fifth gas contains silicon atoms and contains chlorine atoms or hydrogen atoms. The fifth gas includes SiCl ₄ gas or SiH ₄ gas. The fifth gas is, for example, a mixed gas containing SiCl ₄ gas or SiH ₄ gas, Ar gas, and oxygen gas. In step ST121, the fifth gas is supplied from the gas supply unit 44 to the chamber 12c. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Further, high frequency power is supplied from the high frequency power supply 70A and the high frequency power supply 70B to the inner antenna element 52A and the outer antenna element 52B, respectively. A high frequency for bias from the high frequency power supply 30 may be supplied to the lower electrode 18. In step ST121, the fifth gas is excited and plasma is generated. Then, the second film SF2 is formed on the first film SF1 by silicon and oxygen from the plasma. In the subsequent step ST122, the chamber 12c is purged. The purge in step ST122 is the same as the purge in step STST11b.

  Step ST12B includes step ST125, step ST126, step ST127, and step ST128. Process ST125, process ST126, process ST127, and process ST128 constitute sequence SQ12. In step ST12B, the sequence SQ12 is executed once or more.

In step ST125, the sixth gas is supplied to the chamber 12c. The sixth gas includes silicon atoms and chlorine atoms. The sixth gas may be a mixed gas including, for example, SiCl ₄ gas and Ar gas. In step ST125, the sixth gas is supplied from the gas supply unit 44 to the chamber 12c. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. In step ST125, plasma is not generated. In step ST125, molecules containing silicon in the sixth gas are attached to the surface of the first film SF1 as a precursor. In the subsequent step ST126, the chamber 12c is purged. The purge in step ST126 is the same as the purge in step ST11b. By performing step ST126, molecules excessively attached to the first film SF1 can be removed.

  In the subsequent step ST127, the plasma of the seventh gas is generated in the chamber 12c. The seventh gas includes a gas containing oxygen atoms. The seventh gas is a mixed gas containing, for example, oxygen gas and Ar gas. In step ST127, the seventh gas is supplied from the gas supply unit 44 to the chamber 12c. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Further, high frequency power is supplied from the high frequency power supply 70A and the high frequency power supply 70B to the inner antenna element 52A and the outer antenna element 52B, respectively. A high frequency for bias from the high frequency power supply 30 may be supplied to the lower electrode 18. In step ST127, the seventh gas is excited and plasma is generated. The precursor layer is then exposed to oxygen active species from the plasma. Thus, the precursor layer becomes a silicon oxide film (second film SF2 or a part thereof). In the subsequent step ST128, the chamber 12c is purged. The purge in step ST128 is the same as the purge in step ST11b.

  In a subsequent step ST129, it is determined whether or not to end the execution of the sequence SQ12. Specifically, in step ST129, it is determined whether or not the number of executions of sequence SQ12 has reached a preset number. If it is determined in step ST129 that the number of executions of the sequence SQ12 has not reached the preset number, the sequence SQ12 is executed again. On the other hand, if it is determined in step ST129 that the number of executions of sequence SQ12 has reached a preset number, the execution of step ST12B is terminated. The film thickness of the second film SF2 is defined by the number of executions of the sequence SQ12. That is, the film thickness of the second film SF2 increases as the number of executions of the sequence SQ12 increases. The number of executions of the sequence SQ12 is set according to the desired film thickness of the second film SF2.

  Returning to FIG. 17, in the method MTC, the process ST13 is then executed. In step ST13, anisotropic etching is performed on the first film SF1 and the second film SF2. Thereby, the first film SF1 and the second film SF2 on one or more of the plurality of convex regions are removed. For example, as shown in FIG. 21, the first film SF1 and the second film SF2 on the end surface TE1 of the convex region PJ1 are removed.

In step ST13, plasma of the eighth gas is generated in the chamber 12c. The eighth gas can include a fluorocarbon-based gas. The fluorocarbon-based gas includes fluorocarbon (CxFy) and / or hydrofluorocarbon (CxHyFz). The fluorocarbon-based gas can include, for example, one or more of CF ₄ , C ₄ F ₈ , and CHF ₃ . In step ST13, the fourth gas is supplied from the gas supply unit 44 to the chamber 12c. Further, the exhaust device 38 sets the pressure in the chamber 12c to a designated pressure. Further, high frequency power is supplied from the high frequency power supply 70A and the high frequency power supply 70B to the inner antenna element 52A and the outer antenna element 52B, respectively. Further, a high frequency for bias from the high frequency power supply 30 is supplied to the lower electrode 18. Thereby, ions from the plasma are attracted to the workpiece W, and anisotropic etching of the first film SF1 and the second film SF2 is performed.

  The composite film including the first film SF1 and the second film SF2 formed at a position where the distance from the main surface UL1 is small is thin, and the first film SF1 formed at a position where the distance from the main surface UL1 is large. The composite film including the second film SF2 is thick. Therefore, in step ST13, it is possible to remove the composite film on a part of the end surfaces having a small distance from the main surface UL1 among the end surfaces of the plurality of convex regions. For example, as shown in FIG. 21, the first film SF1 and the second film SF2 on the end surface TE1 of the convex region PJ1 are removed. The second film SF2 on the end surface TE2 of the convex region PJ2 is left with a thin film thickness. The remaining first film SF1 and second film SF2 become the second region.

  In subsequent step ST14, the first film SF1 and the second film SF2, that is, the second region, are selectively etched into the first region, that is, the convex region where the end surface is exposed among the plurality of convex regions. Is done. In step ST14, the sequence including the above-described steps ST1 and ST2 is executed once or more. In step ST1, a partial region including the end surface of the convex region where the end surface is exposed among the plurality of convex regions is modified. For example, as shown in FIG. 22, a partial region of the convex region PJ1 including the end surface TE1 is modified to become a modified region MX. In the subsequent step ST2, as shown in FIG. 23, the modified region MX is selectively removed.

  This method MTC can be used not only for etching a part of the convex region of the workpiece W shown in FIG. 18 but also for manufacturing a Fin-type field effect transistor, for example. In manufacturing a Fin-type field effect transistor, a workpiece includes a fin region and a plurality of gate regions. The fin region provides a source region, a drain region, and a channel region. The plurality of gate regions are arranged on the fin region. Between adjacent gate regions, the fin region is covered with a silicon nitride film. In manufacturing a Fin-type field effect transistor, a process of removing a silicon nitride film and exposing a fin region (a source region and a drain region) is performed between adjacent gate regions while protecting a plurality of gate regions. . This process is performed to form a contact with the fin region (source region and drain region). For this process, the method MTC can be used.

  Although various embodiments have been described above, various modifications can be made without being limited to the above-described embodiments. The plasma processing apparatus 10 described above is an inductively coupled plasma processing apparatus, but a plasma processing apparatus that can be used in each of the methods according to various embodiments and modifications thereof is an ECR (Electron Cyclotron Resonance) type plasma. It may be a processing apparatus, a capacitively coupled plasma processing apparatus, or a plasma processing apparatus that uses surface waves such as microwaves in plasma generation.

  DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus, 12 ... Chamber main body, 12c ... Chamber, 14 ... Stage, 16 ... Electrostatic chuck, 18 ... Lower electrode, 30 ... High frequency power supply, 44 ... Gas supply part, 50 ... Antenna, 70A, 70B ... High frequency Power supply, 80 ... control unit, W ... workpiece, R1 ... first region, R2 ... second region, R3 ... third region, MR1 ... modified region, MR3 ... oxidized region.

Claims (16)

A method of selectively etching a first region formed from silicon nitride with respect to a second region formed from silicon oxide,
Preparing a workpiece having the first region and the second region in a chamber provided by a chamber body of a plasma processing apparatus;
Generating a plasma of a first gas containing a gas containing hydrogen in the chamber so as to form a modified region by reforming a part of the first region with active species of hydrogen;
Generating a plasma of a second gas containing a fluorine-containing gas in the chamber so as to remove the modified region by an active species of fluorine;
Including methods. In the chamber, the workpiece is mounted on a stage including an electrode to which a high frequency for drawing ions into the workpiece can be supplied,
In the step of generating the plasma of the first gas, the high frequency is supplied to the electrode.
The method of claim 1. In the chamber, the workpiece is mounted on a stage including an electrode to which a high frequency for drawing ions into the workpiece can be supplied,
In the step of generating the plasma of the second gas, the high frequency is not supplied to the electrode.
The method of claim 1. The method according to claim 1, wherein the second gas includes NF ₃ gas as the gas containing fluorine. The second gas further comprises hydrogen;
The method according to claim 1, wherein a ratio of the number of hydrogen atoms in the second gas to the number of fluorine atoms in the second gas is 8/9 or more. . The method of claim 4, wherein the second gas further comprises H ₂ gas. The method according to claim 6, wherein a ratio of a flow rate of the H ₂ gas in the _second gas to a flow rate of the NF ₃ gas in the _second gas is 3/4 or more. The method according to claim 1, wherein the first gas includes H ₂ gas as the gas containing hydrogen.   The method according to claim 1, wherein a plurality of sequences each including the step of generating the plasma of the first gas and the step of generating the plasma of the second gas are sequentially performed. . The workpiece further includes a third region formed of silicon,
The first gas further includes a gas containing oxygen.
The method according to any one of claims 1 to 9.   The method according to claim 10, wherein the first region is provided so as to cover the second region and the third region. A plurality of sequences each including the step of generating the plasma of the first gas and the step of generating the plasma of the second gas are sequentially executed.
The workpiece further includes a third region formed from silicon,
Before the execution of the plurality of sequences, the first area is provided to cover the second area and the third area,
The plurality of sequences are one or more first sequences executed immediately before the third region is exposed or until the third region is exposed, and one or more executed after the one or more first sequences. The one or more second sequences for oxidizing the surface of the third region,
In at least one or more second sequences, the first gas further includes a gas containing oxygen.
The method according to claim 1.   13. The method of claim 12, wherein in the one or more first sequences, the first gas does not include the gas containing oxygen.   The plurality of sequences further includes one or more third sequences executed after the one or more second sequences, and in the one or more third sequences, the first gas is the gas containing oxygen. The method according to claim 12 or 13, wherein the method is not contained.   The ratio of the flow rate of the gas containing oxygen in the first gas to the flow rate of the gas containing hydrogen in the first gas is 3/100 or more and 9/100 or less. The method according to any one of the above. The method according to claim 10, wherein the gas containing oxygen is O ₂ gas.

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