JP2016136606A - Etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method capable of etching a first region composed of silicon oxide to a second region composed of silicon nitride while suppressing blocking of an opening.SOLUTION: A method of an embodiment includes: (a) a first step of generating plasma of a process gas containing a fluorocarbon gas in a processing container housing a workpiece and forming a deposit containing a fluorocarbon on the workpiece; (b) a second step of generating plasma of a process gas containing an oxygen-containing gas and an inert gas in the processing container housing the workpiece; and (c) a third step of etching a first region by radical of a fluorocarbon contained in the deposit. This method repeatedly performs a sequence including the first step, the second step, and the third step.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to an etching method, and in particular, a first region made of silicon oxide is selectively used with respect to a second region made of silicon nitride by plasma treatment of an object to be processed. The present invention relates to a method for etching.

In manufacturing an electronic device, a process of forming an opening such as a hole or a trench may be performed on a region formed of silicon oxide (SiO ₂ ). In such a process, as described in US Pat. No. 7,708,859, generally, an object to be processed is exposed to a plasma of fluorocarbon gas, and the region is etched.

  Further, a technique for selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride is known. As an example of such a technique, a SAC (Self-Align Contact) technique is known. The SAC technique is described in Japanese Patent Application Laid-Open No. 2000-307001.

  A target object to be processed by the SAC technique has a first region made of silicon oxide, a second region made of silicon nitride, and a mask. The second region is provided so as to define a concave portion, the first region is provided so as to fill the concave portion and cover the second region, and the mask is provided on the first region. And provides an opening over the recess. In the conventional SAC technique, as described in JP 2000-307001 A, plasma of a processing gas containing a fluorocarbon gas, an oxygen gas, and a rare gas is used for etching the first region. By exposing the object to be processed to the plasma of the processing gas, the first region is etched in the portion exposed from the opening of the mask to form the upper opening. Further, when the object to be processed is exposed to the plasma of the processing gas, the portion surrounded by the second region, that is, the first region in the recess is etched in a self-aligned manner. Thereby, a lower opening continuous with the upper opening is formed in a self-aligning manner.

US Patent No. 7,708,859 JP 2000-307001 A

  In the above-described conventional technique, when the etching of the first region proceeds, the deposits derived from the fluorocarbon narrow the opening of the mask and / or the opening formed by the etching of the first region. These openings can be occluded. As a result, the etching rate of the first region decreases, and in some cases, the etching of the first region may stop.

  Accordingly, it is required to etch the first region made of silicon oxide with respect to the second region made of silicon nitride while preventing the opening from being blocked.

  In one embodiment, there is provided a method of selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride by plasma treatment on an object to be processed. The object to be processed includes a second region that defines a concave portion, a first region that fills the concave portion and covers the second region, and a mask that is provided on the first region. This method is (a) a first step of generating a plasma of a processing gas containing a fluorocarbon gas in a processing container containing the target object, and forming a deposit containing the fluorocarbon on the target object. One step, (b) a second step of generating plasma of a processing gas containing an oxygen-containing gas and an inert gas in a processing container containing the object to be processed, and (c) a radical of fluorocarbon contained in the deposit And a third step of etching the first region. In this method, a sequence including the first step, the second step, and the third step is repeatedly executed.

  In the method according to the above aspect, a deposit containing a fluorocarbon is formed on the surface of the object to be processed in the first step, and the first region is etched by the radical of the fluorocarbon in the deposit in the third step. The sequence including the first step and the third step is repeatedly executed. In this method, the amount of deposits is appropriately reduced by using the oxygen active species by executing the second step. Therefore, it is possible to prevent the opening of the mask and the opening formed by etching the first region from being blocked. Further, in this method, since the oxygen-containing gas is diluted with the inert gas in the processing gas, it is possible to suppress the deposits from being excessively removed.

  In one embodiment, the mask is made of an organic material, and a silicon-containing antireflection film is provided on the mask. The method of this embodiment is (d) a fourth step of generating plasma of a processing gas containing fluorocarbon in the processing container, and the first step is performed until the second region is exposed just before the second region is exposed. And (e) a fifth step of generating plasma of the processing gas containing the oxygen-containing gas in the processing container. The sequence is executed after the fourth step and the fifth step. In this embodiment, in the fourth step, the silicon-containing antireflection film is removed simultaneously with the etching of the first region. Then, the width of the opening of the mask is widened by the active species of oxygen generated in the fifth step. Thereby, even if deposits adhere to the surface of the mask that defines the opening, it is possible to reduce the reduction amount of the width of the opening.

  In one embodiment, one second step may be performed for 2 seconds or more, and the deposit may be etched at a rate of 1 nm / second or less in the second step. In order to execute the sequence using the plasma processing apparatus, it takes time to switch the gas for transition between the first to third steps. Therefore, the second step needs to be performed for 2 seconds or more. However, if the etching rate of the second step having such a long time is too high, the deposit for protecting the second region is excessively removed. obtain. By etching the deposit at a rate of 1 nm / second or less in the second step, it is possible to appropriately adjust the amount of the deposit formed on the object to be processed.

  In the sequence of one embodiment, the second step is executed between the first step and the third step, and the sequence is a processing gas containing an oxygen-containing gas and an inert gas in a processing container containing an object to be processed. Another step of generating the plasma may be further included. During the execution of the third step, the material constituting the deposit that has adhered to the object to be processed is released, and the material adheres again to the object to be processed, and is formed by opening the mask and etching the first region. Deposits are formed so as to reduce the width of the openings formed, and in some cases, the deposits may block these openings. According to this embodiment, since the object to be processed is exposed to the active species of oxygen after the execution of the third step, it is possible to reduce the deposit that narrows the width of the opening, and more reliably prevent the opening from being blocked. It becomes possible.

  As described above, the first region made of silicon oxide can be etched with respect to the second region made of silicon nitride while preventing the opening from being blocked.

3 is a flowchart illustrating an etching method according to an embodiment. It is sectional drawing which illustrates the to-be-processed object which is the application object of the etching method which concerns on one Embodiment. It is a figure which shows roughly an example of the plasma processing apparatus which can be used for implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is sectional drawing which shows the to-be-processed object in the middle stage of implementation of the method shown in FIG. It is a flowchart which shows the etching method which concerns on another embodiment. It is sectional drawing which shows the to-be-processed object after execution of process ST14 of the method shown in FIG. It is sectional drawing which shows the to-be-processed object after execution of process ST14 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.

  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 flowchart illustrating an etching method according to an embodiment. A method MT shown in FIG. 1 is a method of selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride by a plasma treatment for an object to be processed.

  FIG. 2 is a cross-sectional view illustrating a target object to which the etching method according to an embodiment is applied. As shown in FIG. 2, the object to be processed, that is, the wafer W has a substrate SB, a first region R1, a second region R2, and an organic film OL that later constitutes a mask. In one example, the wafer W is obtained during the manufacturing of the fin-type field effect transistor, and further includes a raised region RA, a silicon-containing antireflection film AL, and a resist mask RM.

The raised area RA is provided so as to rise from the substrate SB. The raised area RA can constitute, for example, a gate area. The second region R2 is made of silicon nitride (Si ₃ N ₄ ), and is provided on the surface of the raised region RA and the surface of the substrate SB. As shown in FIG. 2, the second region R2 extends so as to define a recess. In one example, the depth of the recess is about 150 nm and the width of the recess is about 20 nm.

The first region R1 is made of silicon oxide (SiO ₂ ) and is provided on the second region R2. Specifically, the first region R1 is provided so as to fill a concave portion defined by the second region R2 and cover the second region R2.

  The organic film OL is provided on the first region R1. The organic film OL can be made of an organic material such as amorphous carbon. The antireflection film AL is provided on the organic film OL. The resist mask RM is provided on the antireflection film AL. The resist mask RM provides an opening having a width wider than the width of the recess on the recess defined by the second region R2. The width of the opening of the resist mask RM is, for example, 60 nm. Such a pattern of the resist mask RM is formed by a photolithography technique.

  In the method MT, an object to be processed such as the wafer W shown in FIG. 2 is processed in the plasma processing apparatus. FIG. 3 is a diagram schematically showing an example of a plasma processing apparatus that can be used to implement the method shown in FIG. A plasma processing apparatus 10 shown in FIG. 3 is a capacitively coupled plasma etching apparatus, and includes a substantially cylindrical processing container 12. The inner wall surface of the processing container 12 is made of anodized aluminum, for example. 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 support portion 14 extends in the vertical direction from the bottom of the processing container 12 in the processing container 12. In addition, 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 thereof. The mounting table PD includes 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, for example, 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 an electrode which is a conductive film is disposed between a pair of insulating layers or 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 by 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 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. In this way, the refrigerant is circulated between the refrigerant flow path 24 and the chiller unit. 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.

  In addition, 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. In one embodiment, the upper electrode 30 may be configured such that the distance in the vertical direction from the upper surface of the mounting table PD, that is, the wafer mounting surface, is variable. 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 is made of silicon.

  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 36b communicating with the gas discharge holes 34a extend downward from the gas diffusion chamber 36a. 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 includes a plurality of gas sources. In one example, the gas source group 40 includes one or more fluorocarbon gas sources, rare gas sources, nitrogen gas (N ₂ gas) sources, hydrogen gas (H ₂ gas) sources, and oxygen-containing gas sources. Contains. The source of one or more fluorocarbon gases may include, in one example, a source of C ₄ F ₈ gas, a source of CF ₄ gas, and a source of C ₄ F ₆ gas. The source of noble gas can be any noble gas source such as He gas, Ne gas, Ar gas, Kr gas, Xe gas, and in one example is a source of Ar gas. Further, the source of the oxygen-containing gas may be a source of oxygen gas (O ₂ gas) in one example. The oxygen-containing gas may be any gas containing oxygen, for example, a carbon oxide gas such as CO gas or CO ₂ gas.

  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. The plurality of gas sources of the gas source group 40 are connected to the gas supply pipe 38 via the corresponding valve of the valve group 42 and the corresponding flow rate controller of the flow rate controller group 44, respectively.

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 .

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. Further, 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 high-frequency power for plasma generation. For example, the first high-frequency power source 62 that generates high-frequency power with a frequency of 27 to 100 MHz is connected to the upper electrode via the matching unit 66. 30. 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 (upper electrode 30 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 high-frequency bias power for drawing ions into the wafer W. For example, the second high-frequency power source 64 generates high-frequency bias power having a frequency in the range of 400 kHz to 13.56 MHz. 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. In another example, the power source 70 may be an AC power source that generates an AC voltage having a relatively low frequency. The voltage applied from the power source 70 to the upper electrode may be a voltage of −150V or less. That is, the voltage applied to the upper electrode 30 by the power source 70 may be a negative voltage having an absolute value of 150 or more. 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. The released silicon is combined with the active species of fluorine existing in the processing space S, and the amount of active species of fluorine is reduced.

  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. In this control unit Cnt, an operator can perform a command input operation and the like to manage the plasma processing apparatus 10 using the input device, and the operating status of the plasma processing apparatus 10 is visualized by the display device. Can be displayed. Furthermore, the storage unit of the control unit Cnt has a control program for controlling various processes executed by the plasma processing apparatus 10 by the processor, and causes each part of the plasma processing apparatus 10 to execute processes according to processing conditions. A program, that is, a processing recipe is stored.

  Hereinafter, the method MT will be described in detail with reference to FIG. 1 again. In the following description, FIGS. 2 and 4 to 16 are referred to as appropriate. 4-16 is sectional drawing which shows the to-be-processed object in the middle stage of implementation of method MT. In the following description, an example in which the wafer W shown in FIG. 2 is processed using one plasma processing apparatus 10 shown in FIG. 3 in the method MT will be described.

  First, in the method MT, the wafer W shown in FIG. 2 is loaded into the plasma processing apparatus 10, and the wafer W is placed on the placement table PD and held by the placement table PD.

In the method MT, step ST1 is then performed. In step ST1, the antireflection film AL is etched. For this reason, in process ST1, processing gas is supplied in processing container 12 from a gas source selected among a plurality of gas sources of gas source group 40. This processing gas contains a fluorocarbon gas. The fluorocarbon gas can include, for example, one or more of C ₄ F ₈ gas and CF ₄ gas. Further, the processing gas may further include a rare gas, for example, Ar gas. In process ST1, exhaust device 50 is operated and the pressure in processing container 12 is set as a predetermined pressure. Further, in step ST1, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30, and high frequency bias power from the second high frequency power supply 64 is supplied to the lower electrode LE.

Below, various conditions in process ST1 are illustrated.
-Processing container pressure: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)
Processing gas C ₄ F ₈ gas: 10 sccm to 30 sccm
CF ₄ gas: 150 sccm to 300 sccm
Ar gas: 200 sccm to 500 sccm
・ High frequency power for plasma generation: 300W to 1000W
・ High frequency bias power: 200W to 500W

  In the process ST1, plasma of the processing gas is generated, and the antireflection film AL is etched in the portion exposed from the opening of the resist mask RM by the active species of fluorocarbon. As a result, as shown in FIG. 4, the portion exposed from the opening of the resist mask RM is removed from the entire region of the antireflection film AL. That is, the pattern of the resist mask RM is transferred to the antireflection film AL, and a pattern providing an opening is formed in the antireflection film AL. In addition, operation | movement of each part of the plasma processing apparatus 10 mentioned above in process ST1 can be controlled by the control part Cnt.

  In the subsequent step ST2, the organic film OL is etched. For this reason, in process ST2, processing gas is supplied in processing container 12 from a gas source selected among a plurality of gas sources of gas source group 40. The processing gas can include hydrogen gas and nitrogen gas. Note that the processing gas used in step ST2 may be another gas, for example, a processing gas containing oxygen gas, as long as it can etch the organic film. Moreover, in process ST2, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST2, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30, and high frequency bias power from the second high frequency power supply 64 is supplied to the lower electrode LE.

Below, various conditions in process ST2 are illustrated.
-Processing container pressure: 50 mTorr (6.65 Pa) to 200 mTorr (26.6 Pa)
Process gas N ₂ gas: 200 sccm to 400 sccm
H ₂ gas: 200 sccm to 400 sccm
・ High frequency power for plasma generation: 500W to 2000W
・ High frequency bias power: 200W to 500W

  In step ST2, plasma of the processing gas is generated, and the organic film OL is etched in a portion exposed from the opening of the antireflection film AL. The resist mask RM is also etched. As a result, as shown in FIG. 5, the resist mask RM is removed, and the portion exposed from the opening of the antireflection film AL is removed from the entire region of the organic film OL. That is, the pattern of the antireflection film AL is transferred to the organic film OL, the pattern that provides the opening MO is formed in the organic film OL, and the mask MK is generated from the organic film OL. In addition, operation | movement of each part of the plasma processing apparatus 10 mentioned above in process ST2 can be controlled by the control part Cnt.

  In one embodiment, step ST3 is performed after step ST2. In step ST3, the first region R1 is etched until just before the second region R2 is exposed. That is, the first region R1 is etched until the first region R1 remains slightly on the second region R2. For this reason, in process ST3, process gas is supplied in process container 12 from a gas source selected among a plurality of gas sources of gas source group 40. This processing gas contains a fluorocarbon gas. Further, the processing gas may further include a rare gas, for example, Ar gas. The processing gas may further include oxygen gas. Moreover, in process ST3, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST3, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30, and high frequency bias power from the second high frequency power supply 64 is supplied to the lower electrode LE.

  In step ST3, plasma of the processing gas is generated, and the first region R1 is etched by the active species of fluorocarbon in the portion exposed from the opening of the mask MK. The processing time of this step ST3 is set so that the first region R1 is left with a predetermined film thickness on the second region R2 at the end of the step ST3. As a result of the execution of this step ST3, the upper opening UO is partially formed as shown in FIG. In addition, operation | movement of each part of the plasma processing apparatus 10 mentioned above in process ST3 can be controlled by the control part Cnt.

Here, in step ST11 to be described later, a mode in which the formation of a deposit containing fluorocarbon is more advantageous on the surface of the wafer W including the first region R1 than the etching of the first region R1, that is, the deposition mode is set. A condition is selected. On the other hand, in the process ST3, a mode in which the etching of the first region R1 is superior to the formation of the deposit, that is, a condition for the etching mode is selected. Thus, in one example, the fluorocarbon gas to be utilized in step ST3 may include one or more of the C ₄ F ₈ gas and CF ₄ gas. The fluorocarbon gas in this example has a ratio of the number of fluorine atoms to the number of carbon atoms (that is, the number of fluorine atoms / the number of carbon atoms) (that is, the number of fluorine atoms / the number of carbon atoms) of the fluorocarbon gas used in step ST11 (that is, the number of carbon atoms). , Fluorine carbon number / carbon atom number). In one example, in order to increase the degree of dissociation of the fluorocarbon gas, the high frequency power for plasma generation used in step ST3 can be set to a higher power than the high frequency power for plasma generation used in step ST11. According to these examples, the etching mode can be realized. In one example, the high-frequency bias power used in step ST3 can also be set to be higher than the high-frequency bias power in step ST11. According to this example, the energy of ions drawn into the wafer W is increased, and the first region R1 can be etched at a high speed.

Below, various conditions in process ST3 are illustrated.
-Processing container pressure: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)
Processing gas C ₄ F ₈ gas: 10 sccm to 30 sccm
CF ₄ gas: 50 sccm to 150 sccm
Ar gas: 500 sccm to 1000 sccm
O ₂ gas: 10 sccm to 30 sccm
・ High frequency power for plasma generation: 500W to 2000W
・ High frequency bias power: 500W to 2000W

  In one embodiment, process ST4 is then performed. In step ST4, plasma of a processing gas containing an oxygen-containing gas is generated in the processing container 12. For this reason, in process ST4, process gas is supplied in process container 12 from a gas source selected among a plurality of gas sources of gas source group 40. In one example, the processing gas may include oxygen gas as the oxygen-containing gas. Further, the processing gas may further include an inert gas such as a rare gas (for example, Ar gas) or nitrogen gas. Moreover, in process ST4, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST <b> 4, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30. In step ST4, the high frequency bias power from the second high frequency power supply 64 may not be supplied to the lower electrode LE.

  In step ST4, oxygen active species are generated, and the opening MO of the mask MK is widened at the upper end portion by the oxygen active species. Specifically, as shown in FIG. 7, etching is performed so that the upper shoulder portion of the mask MK that defines the upper end portion of the opening MO has a tapered shape. Thereby, even if the deposit generated in the subsequent process adheres to the surface defining the opening MO of the mask MK, the reduction amount of the width of the opening MO can be reduced. In addition, operation | movement of each part of the plasma processing apparatus 10 mentioned above in process ST4 can be controlled by the control part Cnt.

  Here, in step ST12 to be described later, a very small amount of deposit formed in each sequence is reduced, and it is necessary to suppress an excessive decrease in the deposit. On the other hand, in step ST4, the process is performed to increase the width of the upper end portion of the opening MO of the mask MK, and a short processing time is required.

Below, various conditions in process ST4 are illustrated.
・ Processing vessel internal pressure: 30 mTorr (3.99 Pa) to 200 mTorr (26.6 Pa)
Processing gas O ₂ gas: 50 sccm to 500 sccm
Ar gas: 200 sccm to 1500 sccm
・ High frequency power for plasma generation: 100 W to 500 W
・ High frequency bias power: 0W to 200W

  Next, in the method MT, the sequence SQ is repeatedly performed to etch the first region R1. The sequence SQ includes a process ST11, a process ST12, and a process ST13 in order.

  In sequence SQ, step ST11 is first executed. In step ST11, plasma of a processing gas is generated in the processing container 12 in which the wafer W is accommodated. For this reason, in process ST11, process gas is supplied in process container 12 from a gas source selected among a plurality of gas sources of gas source group 40. This processing gas contains a fluorocarbon gas. Further, the processing gas may further include a rare gas, for example, Ar gas. Moreover, in process ST11, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST <b> 11, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30. As a result, plasma of the processing gas containing the fluorocarbon gas is generated, and the dissociated fluorocarbon is deposited on the surface of the wafer W to form a deposit DP as shown in FIG. The operation of each part of the above-described plasma processing apparatus 10 in the step ST11 can be controlled by the control unit Cnt.

As described above, in step ST11, the conditions for the deposition mode are selected. For this reason, in one example, C ₄ F ₆ gas is used as the fluorocarbon gas.

Below, various conditions in process ST11 are illustrated.
-Processing container pressure: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)
Processing gas C ₄ F ₆ gas: 2 sccm to 10 sccm
Ar gas: 500 sccm to 1500 sccm
・ High frequency power for plasma generation: 100 W to 500 W
・ High frequency bias power: 0W

  Next, in method MT, step ST12 is performed. In step ST12, plasma of a processing gas containing an oxygen-containing gas and an inert gas is generated in the processing container 12. For this reason, in process ST12, process gas is supplied in process container 12 from a gas source selected among a plurality of gas sources of gas source group 40. In one example, the processing gas includes oxygen gas as the oxygen-containing gas. In one example, the processing gas includes a rare gas such as Ar gas as an inert gas. The inert gas may be nitrogen gas. Moreover, in process ST12, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST <b> 12, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30. In step ST12, the high frequency bias power from the second high frequency power supply 64 may not be supplied to the lower electrode LE.

  In step ST12, active species of oxygen are generated, and the amount of deposit DP on the wafer W is appropriately reduced by the active species of oxygen as shown in FIG. As a result, the opening MO and the upper opening UO are prevented from being blocked by the excessive deposit DP. Further, in the processing gas used in step ST12, since the oxygen gas is diluted with the inert gas, it is possible to suppress the deposit DP from being excessively removed. The operation of each part of the above-described plasma processing apparatus 10 in step ST12 can be controlled by the control unit Cnt.

Below, various conditions in process ST12 are illustrated.
-Processing container pressure: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)
Process gas O ₂ gas: ₂ sccm to 20 sccm
Ar gas: 500 sccm to 1500 sccm
・ High frequency power for plasma generation: 100 W to 500 W
・ High frequency bias power: 0W

  In one embodiment, step ST12 of each sequence, that is, one step ST12, is performed for 2 seconds or more, and the deposit DP can be etched at a rate of 1 nm / second or less in step ST12. In order to execute the above sequence using a plasma processing apparatus such as the plasma processing apparatus 10, it takes time to switch gases for transition between the processes ST11, ST12, and ST13. Therefore, considering the time required for stable discharge, the step ST12 needs to be executed for 2 seconds or more. However, if the etching rate of the deposit DP in such a long time period is too high, the deposit for protecting the second region R2 may be excessively removed. For this reason, the deposit DP is etched at a rate of 1 nm / second or less in the step ST12. Thereby, the amount of the deposit DP formed on the wafer W can be adjusted appropriately. Note that the rate of etching of the deposit DP in the process ST12 of 1 nm / second or less is the pressure in the processing container, the degree of dilution of the oxygen in the processing gas with the rare gas, that is, the oxygen concentration, and the high frequency for plasma generation. Power can be achieved by selecting from the conditions described above.

  In subsequent step ST13, the first region R1 is etched. For this reason, in process ST13, processing gas is supplied in processing container 12 from a gas source selected among a plurality of gas sources of gas source group 40. This processing gas contains an inert gas. In one example, the inert gas may be a noble gas such as Ar gas. Alternatively, the inert gas may be nitrogen gas. Moreover, in process ST13, the exhaust apparatus 50 is operated and the pressure in the processing container 12 is set to a predetermined pressure. Further, in step ST <b> 13, high frequency power from the first high frequency power supply 62 is supplied to the upper electrode 30. In step ST13, the high frequency bias power from the second high frequency power supply 64 is supplied to the lower electrode LE.

Below, various conditions in process ST13 are illustrated.
-Processing container pressure: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)
Processing gas Ar gas: 500 sccm to 1500 sccm
・ High frequency power for plasma generation: 100 W to 500 W
・ High frequency bias power: 20W to 300W

  In step ST <b> 13, an inert gas plasma is generated and ions are attracted to the wafer W. Then, the first region R1 is etched by the fluorocarbon radicals contained in the deposit DP. As a result, as shown in FIG. 10, the first region R1 in the recess provided by the second region R2 is etched, and the lower opening LO is gradually formed. The operation of each part of the plasma processing apparatus 10 described above in step ST13 can be controlled by the control unit Cnt.

  In the method MT, the sequence SQ including the above-described steps ST11 to ST13 is repeated. As the sequence SQ is repeated, the deposit DP is formed on the wafer W by executing the step ST11 as shown in FIG. Then, as shown in FIG. 12, the amount of the deposit DP is reduced by executing the step ST12. And as shown in FIG. 13, 1st area | region R1 is further etched by execution of process ST13, and the depth of lower opening LO becomes deep. As the sequence SQ is further repeated, a deposit DP is formed on the wafer W by executing the step ST11 as shown in FIG. And as shown in FIG. 15, the quantity of deposit DP is reduced by execution of process ST12. And as shown in FIG. 16, 1st area | region R1 is further etched by execution of process ST13, and the depth of lower opening LO becomes deeper. Finally, the first region R1 is etched until the second region R2 at the bottom of the recess is exposed.

  Returning to FIG. 1, in the method MT, it is determined whether or not the stop condition is satisfied in the step STa. The stop condition is determined to be satisfied when the sequence SQ is executed a predetermined number of times. In step STa, when it is determined that the stop condition is not satisfied, the sequence SQ is executed from step ST11. On the other hand, when it is determined in the step STa that the stop condition is satisfied, the execution of the method MT ends.

  In one embodiment, the amount by which the first region R1 is etched in a sequence SQ (hereinafter referred to as “first sequence”) executed in a period including when the second region R2 is exposed is executed thereafter. Conditions in the repetition of the sequence SQ may be set so that the amount of the first region R1 is less than the amount etched in the sequence SQ (hereinafter referred to as “second sequence”). In one example, the execution time length of the first sequence is set shorter than the execution time length of the second sequence. In this example, the ratio of the execution time length of the process ST11, the execution time length of the process ST12, and the execution time length of the process ST13 in the first sequence is the execution time length of the process ST11 and the execution time length of the process ST12 in the second sequence. , And the ratio of the execution time length of step ST13. For example, in the first sequence, the execution time length of the process ST11 is selected from a time length in the range of 2 seconds to 5 seconds, and the execution time length of the process ST12 is selected from a time length in the range of 2 seconds to 5 seconds. The execution time length of ST13 is selected from a time length in the range of 5 seconds to 10 seconds. In the second sequence, the execution time length of the process ST11 is selected from a time length in the range of 2 seconds to 10 seconds, and the execution time length of the process ST12 is selected from a time length in the range of 2 seconds to 10 seconds. The execution time length of ST13 is selected from a time length in the range of 5 to 20 seconds.

  The active species of the fluorocarbon generated in the process ST11 is deposited on the second region R2 to protect the second region R2, but when the first region R1 is etched and the second region R2 is exposed, the second region R2 is exposed. Region R2 may be etched. Therefore, in one embodiment, the first sequence is executed in a period in which the second region R2 is exposed. Thereby, the deposit DP is formed on the wafer W while the etching amount is suppressed, and the second region R2 is protected by the deposit DP. Thereafter, the second sequence with a large etching amount is executed. Therefore, according to this embodiment, it is possible to etch the first region R1 while suppressing the scraping of the second region R2.

  In step ST13 of the sequence SQ (hereinafter referred to as “third sequence”) executed after execution of the second sequence, the high-frequency bias power is used in the step ST13 of the first sequence and the second sequence. The power may be set higher than the power. For example, in the process ST13 of the first sequence and the second sequence, the high-frequency bias power is set to 20 W to 100 W, and in the third sequence process ST13, the high-frequency bias power is set to 100 W to 300 W. In the third sequence as an example, the execution time length of the process ST11 is selected from a time length in the range of 2 seconds to 10 seconds, and the execution time length of the process ST12 is selected from a time length in the range of 2 seconds to 10 seconds. The execution time length of step ST13 is selected from a time length in the range of 5 seconds to 15 seconds.

  As shown in FIG. 14, the amount of the deposit DP on the wafer W is considerably increased after the execution of the first sequence and the second sequence. When the amount of the deposit DP increases, the width of the opening MO, the upper opening UO, and the width of the lower opening LO are narrowed by the deposit DP. As a result, a situation may occur where the flux of ions reaching the deep part of the lower opening LO is insufficient. However, in the third sequence step ST13, since a relatively large high-frequency bias power is used, the energy of ions attracted to the wafer W is increased. As a result, even if the lower opening LO is deep, ions can be supplied to the deep part of the lower opening LO.

  Hereinafter, an etching method according to another embodiment will be described. FIG. 17 is a flowchart showing an etching method according to another embodiment. 18 and 19 are cross-sectional views showing the object to be processed after step ST14 of the method shown in FIG. FIG. 18 shows a cross-sectional state of the wafer after the process ST14 is performed on the wafer W shown in FIG. 10, and FIG. 19 shows the process ST14 performed on the wafer W shown in FIG. The state of the cross section of the wafer after being processed is shown. The method MT2 shown in FIG. 17 is different from the method MT in that the sequence SQ further includes a step ST14 executed after the execution of the step ST13. This step ST14 is the same as step ST12. As the conditions in the process of step ST14, the conditions described above regarding the process of step ST12 can be adopted.

  As described above, ions are attracted to the wafer W in the process ST13. As a result, the material constituting the deposit DP is released from the wafer W, and the material adheres to the wafer W again, so that the width of the opening MO and the lower opening LO is reduced as shown in FIGS. 10 and 13. A deposit DP is formed. This deposit DP may block the opening MO and the lower opening LO in some cases. In the method MT2, the wafer W shown in FIGS. 10 and 13 is exposed to the active species of oxygen by the execution of the step ST14 as in the case of the step ST12. As a result, the deposit DP (see FIGS. 10 and 13) that narrows the width of the opening MO and the lower opening LO can be reduced as shown in FIGS. 18 and 19, and the opening MO and the lower opening LO are blocked. Can be prevented more reliably.

  Although various embodiments have been described above, various modifications can be made without being limited to the above-described embodiments. For example, in the implementation of the method MT, high-frequency power for plasma generation is supplied to the upper electrode 30, but the high-frequency power may be supplied to the lower electrode LE. In addition, a plasma processing apparatus other than the plasma processing apparatus 10 can be used for performing the method MT. Specifically, the method MT can be performed using an arbitrary plasma processing apparatus such as an inductively coupled plasma processing apparatus or a plasma processing apparatus that generates plasma by surface waves such as microwaves. .

  In addition, the execution order of the steps ST11, ST12, and ST13 in the sequence SQ of the method MT may be changed. For example, in the sequence SQ of the method MT, the process ST12 may be performed after the process ST13 is performed.

  DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus, 12 ... Processing container, 30 ... Upper electrode, PD ... Mounting stage, LE ... Lower electrode, ESC ... Electrostatic chuck, 40 ... Gas source group, 42 ... Valve group, 44 ... Flow controller group, DESCRIPTION OF SYMBOLS 50 ... Exhaust device, 62 ... 1st high frequency power supply, 64 ... 2nd high frequency power supply, Cnt ... Control part, W ... Wafer, R1 ... 1st area | region, R2 ... 2nd area | region, OL ... Organic film, AL ... Silicon Containing antireflection film, MK ... mask, DP ... deposit.

Claims (4)

A method of selectively etching a first region composed of silicon oxide with respect to a second region composed of silicon nitride by a plasma treatment on an object to be processed,
The object to be processed includes the second region that defines a concave portion, the first region that is provided to fill the concave portion and cover the second region, and a mask that is provided on the first region. Have
The method
A first step of generating plasma of a processing gas containing a fluorocarbon gas in a processing container containing the processing target, and forming a deposit containing the fluorocarbon on the processing target;
A second step of generating plasma of a processing gas containing an oxygen-containing gas and an inert gas in a processing container containing the object to be processed;
A third step of etching the first region with fluorocarbon radicals contained in the deposit;
Including
A method in which a sequence including the first step, the second step, and the third step is repeatedly executed. The mask is made of an organic material,
A silicon-containing antireflection film is provided on the mask,
A fourth step of generating a plasma of a processing gas containing a fluorocarbon gas in the processing container, the fourth step of etching the first region until just before the second region is exposed; and
A fifth step of generating plasma of a processing gas containing an oxygen-containing gas in the processing container;
Further including
The method according to claim 1, wherein the sequence is executed after execution of the fourth step and the fifth step.   3. The method according to claim 1, wherein one second step is performed for 2 seconds or more, and the deposit is etched at a rate of 1 nm / second or less in the second step. In the sequence, the second step is executed between the first step and the third step,
The sequence further includes another step of generating plasma of a processing gas containing an oxygen-containing gas and an inert gas in a processing container containing the object to be processed.
The method according to claim 1.

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