KR20160088816A - Etching method - Google Patents

Abstract

Provided is a method for etching a first region composed of silicon oxide with respect to a second region composed of silicon nitride while preventing blockage of openings. The method according to an embodiment includes: a first process of generating a plasma of a processing gas containing a fluorocarbon gas in a processing chamber where a target object is stored, and forming a deposit containing fluorocarbon on the target object; a second process of generating a plasma of a processing gas containing an oxygen-containing gas and an inert gas in the processing chamber stored with the target object; and a third process of etching the first region by radicals of fluorocarbon contained in the deposit. A sequence including the first, second, and third processes is repeatedly performed.

Description

ETCHING METHOD

An embodiment of the present invention relates to an etching method and more particularly to 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 on the object to be processed .

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

Further, there is known a technique of selectively etching a first region composed of silicon oxide with respect to a second region composed of silicon nitride. As one example of such a technique, a self-aligned contact (SAC) technique is known. SAC technology is disclosed in Japanese Patent Application Laid-Open No. 2000-307001.

The object to be treated by the SAC technology 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 partition the concave portion, the first region is provided to fill the concave portion and also to cover the second region, the mask is provided on the first region, and the opening is provided on the concave portion . In the conventional SAC technique, as described in Japanese Patent Application Laid-Open No. 2000-307001, plasma of a process gas containing fluorocarbon gas, oxygen gas, and rare gas is used for etching the first region. By exposing the object to the plasma of the process gas, the first region is etched in the portion exposed from the opening of the mask to form the upper opening. Further, by exposing the workpiece to the plasma of the process gas, the portion surrounded by the second region, that is, the first region in the recess, is self-alignedly etched. Thus, the lower openings continuous to the upper openings are formed in a self-aligning manner.

(Prior art document)

(Patent Literature)

(Patent Document 1) U.S. Patent No. 7,708,859

(Patent Document 2) Japanese Unexamined Patent Application Publication No. 2000-307001

In the above-mentioned conventional technique, when the etching of the first region proceeds, the opening formed by the opening of the mask and / or the etching of the first region becomes narrow due to the deposits derived from the fluorocarbon, , These openings can be closed. As a result, the etching rate of the first region is lowered, and in some cases, etching of the first region may be stopped.

Therefore, it is required to etch the first region composed of silicon oxide with respect to the second region composed of silicon nitride, while preventing the occlusion of the opening.

In one form, a method of selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride is provided by plasma treatment on the object to be processed. The object to be processed has a second region for partitioning the concave portion, a first region filling the concave portion and covering the second region, and a mask provided on the first region. The method comprises the steps of: (a) a first step of producing a plasma of a process gas containing a fluorocarbon gas in a process container accommodating the process target, the process comprising: forming a deposit containing fluorocarbon on the target object; (B) a second step of producing a plasma of a process gas containing an oxygen-containing gas and an inert gas in a process container containing the process container, (c) a second process of producing a plasma of a fluorocarbon And a third step of etching the first region by radicals of the first region. In this method, the sequence including the first step, the second step, and the third step is repeatedly executed.

The method according to one aspect of the present invention is characterized in that a deposit containing fluorocarbon is formed on the surface of the object to be treated in the first step and the first region is formed by the radical of the fluorocarbon in the deposit in the third step And repeats the sequence including the first step and the third step. And, this method appropriately reduces the amount of sediments using active species of oxygen by executing the second step. Therefore, it becomes possible to prevent the opening of the mask and the clogging of the opening formed by the etching of the first region. Further, in this method, the oxygen-containing gas in the process gas is diluted by the inert gas, and therefore it is possible to suppress the excessive removal of the deposit.

In one embodiment, the mask is made of an organic material, and a silicon-containing antireflection film is provided on the mask. (D) a fourth step of producing a plasma of a process gas containing fluorocarbon in the process container, the process comprising the steps of: etching the first region until immediately before the second region is exposed; 4; and (e) a fifth step of generating a plasma of a process gas containing an oxygen-containing gas in the process container. The sequence is executed after execution of 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. The width of the opening of the mask is enlarged by the active species of oxygen generated in the fifth step. This makes it possible to reduce the amount of reduction in the width of the opening even if the deposit adheres to the surface of the mask partitioning the opening.

In one embodiment, the second step may be performed for 2 seconds or more, and the sediment may be etched at a rate of 1 nm / sec or less in the second step. In order to execute the above-described sequence using the plasma processing apparatus, it takes time to switch the gas for transition between the respective steps of the first to third steps. Thus, although the second process needs to be performed for 2 seconds or more, if the rate of etching in the second step of such a time length is too high, the deposit for protecting the second region can be over-removed. In the second step, the deposit is etched at a rate of 1 nm / sec or less, whereby the amount of the deposit formed on the object to be processed can be appropriately adjusted.

In the sequence of the embodiment, the second step is executed between the first step and the third step, and the sequence is a step of supplying a treatment gas containing an oxygen-containing gas and an inert gas And may further include another process of generating plasma. During the execution of the third step, the substance constituting the deposit deposited on the object to be treated is released, the substance is reattached to the object to be processed, and the opening of the mask and the opening formed by the etching of the first region Deposits may be formed to narrow the width, and in some cases, the deposit may occlude these openings. According to this embodiment, since the object to be treated is exposed to the active species of oxygen after the execution of the third step, sediments that narrow the opening width can be reduced, and it becomes possible to more reliably prevent the opening from clogging.

As described above, it becomes possible to etch the first region composed of silicon oxide with respect to the second region composed of silicon nitride, while preventing the occlusion of the opening.

1 is a flow diagram illustrating an etching method in accordance with an embodiment.
2 is a cross-sectional view illustrating an object to which an etching method according to an embodiment is applied.
Fig. 3 is a view schematically showing an example of a plasma processing apparatus that can be used in the implementation of the method shown in Fig.
Fig. 4 is a cross-sectional view showing the object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 5 is a cross-sectional view showing an object to be processed in the middle step of the method shown in Fig. 1. Fig.
Fig. 6 is a cross-sectional view showing the object to be processed in the middle step of the method shown in Fig. 1; Fig.
Fig. 7 is a cross-sectional view showing an object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 8 is a cross-sectional view showing the object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 9 is a cross-sectional view showing the object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 10 is a cross-sectional view showing the object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 11 is a cross-sectional view showing the object to be processed in the middle step of the method shown in Fig. 1; Fig.
Fig. 12 is a cross-sectional view showing an object to be processed in the middle step of the method shown in Fig. 1; Fig.
13 is a cross-sectional view showing an object to be processed in the middle step of the method shown in Fig.
Fig. 14 is a cross-sectional view showing an object to be processed in the middle step of the method shown in Fig. 1; Fig.
Fig. 15 is a cross-sectional view showing an object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
Fig. 16 is a cross-sectional view showing an object to be processed in the intermediate step of the method shown in Fig. 1; Fig.
17 is a flowchart showing an etching method according to another embodiment.
18 is a cross-sectional view showing an object to be processed after the execution of step ST14 of the method shown in Fig.
Fig. 19 is a cross-sectional view showing an object to be processed after the execution of step ST14 of the method shown in Fig. 17;

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

1 is a flow diagram illustrating an etching method in accordance with an embodiment. The 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 on the object to be treated.

2 is a cross-sectional view illustrating an object to which an 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 constituting a mask thereafter. In one example, the wafer W is obtained during the manufacture of the pin-type field effect transistor, and further includes the raised region RA, the silicon-containing anti-reflection film AL, and the resist mask RM.

The raised region RA is provided so as to protrude from the substrate SB. The raised region RA can constitute, for example, a gate region. The second region R2 is constituted by a silicon nitride (Si ₃ N _4), it is provided on the surface of the surface of the raised region RA, and the substrate SB. As shown in Fig. 2, the second region R2 is extended so as to divide the concave portion. 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, is composed of a silicon oxide (SiO _2), it is provided on the second region R2. Specifically, the first region R1 is provided so as to fill the concavity 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 may be composed of an organic material, for example, 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 larger than the width of the concave portion on the concave portion divided by the second region R2. The width of the opening of the resist mask RM is, for example, 60 nm. The pattern of the resist mask RM is formed by photolithography.

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 view schematically showing an example of a plasma processing apparatus that can be used in the implementation of the method shown in Fig. The plasma processing apparatus 10 shown in Fig. 3 is a capacitively coupled plasma etching apparatus, and has a substantially cylindrical processing vessel 12. The inner wall surface of the processing vessel 12 is made of, for example, anodized aluminum. The processing vessel 12 is securely grounded.

On the bottom of the processing container 12, a substantially cylindrical support portion 14 is provided. The supporting portion 14 is made of, for example, an insulating material. The support portion 14 extends in the vertical direction from the bottom of the processing vessel 12 in the processing vessel 12. [ In the processing container 12, a mounting table PD is provided. The mount table PD is supported by the support portion 14. [

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

On the second plate 18b, an electrostatic chuck ESC is provided. The electrostatic chuck ESC has a structure in which an electrode serving as a conductive film is disposed between a pair of insulating layers or insulating sheets. A DC power supply 22 is electrically connected to an electrode of the electrostatic chuck ESC via a switch 23. [ The electrostatic chuck ESC sucks 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.

On the periphery of the second plate 18b, a focus ring FR is disposed so as to surround the edge of the wafer W and the electrostatic chuck ESC. The focus ring FR is provided to improve the uniformity of the etching. The focus ring FR is made of a material suitably selected depending on the material of the film to be etched, and may be made of, for example, quartz.

A refrigerant passage (24) is provided in the second plate (18b). The refrigerant flow path 24 constitutes a temperature adjusting mechanism. The refrigerant is supplied to the refrigerant passage 24 from the chiller unit provided outside the processing vessel 12 via the pipe 26a. The refrigerant supplied to the refrigerant passage 24 is returned to the chiller unit via the pipe 26b. Thus, the refrigerant circulates between the refrigerant passage (24) and the chiller unit. By controlling the temperature of the coolant, the temperature of the wafer W supported by the electrostatic chuck ESC is controlled.

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

Further, the plasma processing apparatus 10 includes an upper electrode 30. The upper electrode 30 is arranged on the upper side of the stage PD and opposite to the stage PD. The lower electrode LE and the upper electrode 30 are provided approximately parallel to each other. Between the upper electrode 30 and the lower electrode LE, a processing space S for performing plasma processing on the wafer W is provided.

The upper electrode 30 is supported on the upper portion of the processing container 12 with the insulating shield member 32 interposed therebetween. In one embodiment, the upper electrode 30 can be configured such that the distance in the vertical direction from the upper surface of the mount table PD, that is, the wafer mounting surface, is variable. The upper electrode 30 may 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. The electrode plate 34 is made of silicon in one embodiment.

The electrode support 36 supports the electrode plate 34 in a detachable manner, and may be made of a conductive material such as aluminum. The electrode support 36 may have a water cooling structure. A gas diffusion chamber (36a) is provided in the electrode support (36). From the gas diffusion chamber 36a, a plurality of gas communication holes 36b communicating with the gas discharge holes 34a extend downward. A gas introduction port 36c for introducing a process gas into the gas diffusion chamber 36a is formed in the electrode support 36. 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 controller group 44. The gas source group 40 includes a plurality of gas sources. In one example, the gas source group 40 includes a source of at least one fluorocarbon gas, a source of rare gas, a source of nitrogen gas (N ₂ gas), a source of hydrogen gas (H ₂ gas) Source. The source of the at least one fluorocarbon gas may comprise, in one example, a source of a C ₄ F ₈ gas, a source of a CF ₄ gas, and a source of a C ₄ F ₆ gas. The source of the rare gas may be any of rare gas sources such as He gas, Ne gas, Ar gas, Kr gas, and Xe gas, and in one example, it is a source of Ar gas. Further, the source of the oxygen-containing gas may be, for example, a source of oxygen gas (O ₂ gas). The oxygen-containing gas may be any gas containing oxygen, for example, carbon dioxide gas such as CO gas or CO ₂ gas.

The valve group 42 includes a plurality of valves, and the flow controller group 44 includes a plurality of flow controllers called mass flow controllers. The plurality of gas sources of the gas source group 40 are respectively connected to the gas supply pipe 38 via corresponding valves of the valve group 42 and corresponding flow controllers of the flow controller group 44.

In the plasma processing apparatus 10, a sediment shield 46 is detachably provided along the inner wall of the processing vessel 12. [ The sediment shield 46 is also provided on the outer periphery of the support portion 14. The deposit shield 46 prevents deposition of etching sub-organisms (sediments) on the processing vessel 12 and can be constituted 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 vessel 12 and also between the supporting portion 14 and the side wall of the processing vessel 12. The exhaust plate 48 can be constituted by, for example, coating an aluminum material with ceramics such as Y ₂ O ₃ . An exhaust port 12e 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 decompress the space in the processing container 12 to a desired degree of vacuum. A loading / unloading port 12g of the wafer W is provided on the side wall of the processing container 12, and the loading / unloading port 12g is opened / closed by the 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 for generating high frequency electric power for generating plasma. For example, the first high frequency power source 62 for generating high frequency electric power of a frequency of 27 to 100 MHz includes a matching device 66 And is connected to the upper electrode 30 through the through- The matching unit 66 is a circuit for matching the output impedance of the first high frequency power supply 62 with the input impedance of the load side (the upper electrode 30 side). 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 for generating a high frequency bias power for attracting ions to the wafer W and generates a high frequency bias power having a frequency within a range of 400 kHz to 13.56 MHz, for example. 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 supply 64 with the input impedance of the load side (lower electrode LE side).

Further, 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 to draw the positive ions present in the processing space S to 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 a relatively low-frequency AC voltage. The voltage applied from the power source 70 to the upper electrode may be a voltage of -150 V or less. That is, the voltage applied to the upper electrode 30 by the power source 70 may be a negative voltage whose absolute value is 150 or more. When such a voltage is applied to the upper electrode 30 from the power source 70, the positive ions existing in the processing space S collide with the electrode plate 34. As a result, secondary electrons and / or silicon is emitted from the electrode plate 34. The released silicon combines with the active species of fluorine present in the processing space S, thereby reducing the amount of active species of fluorine.

Further, in one embodiment, the plasma processing apparatus 10 may further include a control unit Cnt. The control unit Cnt is a computer having a processor, a storage unit, an input unit, a display unit, and the like, and controls each unit of the plasma processing apparatus 10. In this control unit Cnt, an operator can input commands or the like to manage the plasma processing apparatus 10 by using the input device, and the operating condition of the plasma processing apparatus 10 can be determined It can be visualized and displayed. The storage section of the control section Cnt is provided with a control program for controlling various processes executed in the plasma processing apparatus 10 by a processor and a control program for controlling the respective sections of the plasma processing apparatus 10 A program, that is, a processing recipe is stored.

Hereinafter, referring again to FIG. 1, the method MT will be described in detail. In the following description, FIG. 2 and FIG. 4 to FIG. 16 are referred to appropriately. Figs. 4 to 16 are cross-sectional views showing the object to be processed in the middle step of the method MT. Fig. In the following description, an example will be described in which, in the method MT, the wafer W shown in Fig. 2 is processed by using one plasma processing apparatus 10 shown in Fig.

First, in the method MT, the wafer W shown in Fig. 2 is carried into the plasma processing apparatus 10, and the wafer W is loaded on the loading platform PD and held by the loading platform PD.

In the method MT, the next step ST1 is executed. In step ST1, the antireflection film AL is etched. To this end, in process ST1, a process gas is supplied into the process container 12 from a gas source selected from a plurality of gas sources of the gas source group 40. [ This process gas includes a fluorocarbon gas. The fluorocarbon gas may include, for example, at least one of C ₄ F ₈ gas and CF ₄ gas. Further, the process gas may further include a rare gas such as Ar gas. Further, in step ST1, the exhaust apparatus 50 is operated, and the pressure in the processing vessel 12 is set to a predetermined pressure. In step ST1, the high-frequency power from the first high-frequency power source 62 is supplied to the upper electrode 30, and the high-frequency bias power from the second high-frequency power source 64 is supplied to the lower electrode LE.

Various conditions in step ST1 will be exemplified below.

Pressure in the processing vessel: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)

ㆍ Process 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: 300 W to 1000 W

ㆍ High frequency bias power: 200W ~ 500W

In the process ST1, a plasma of the process gas is generated, and the anti-reflection film AL is etched by the active species of the fluorocarbon at a portion exposed from the opening of the resist mask RM. As a result, as shown in Fig. 4, a portion exposed from the opening of the resist mask RM in the entire area of the antireflection film AL is removed. That is, the pattern of the resist mask RM is transferred to the antireflection film AL, and a pattern for providing an opening in the antireflection film AL is formed. The operation of each section of the plasma processing apparatus 10 described above in step ST1 can be controlled by the control section Cnt.

In the next step ST2, the organic film OL is etched. To this end, in process ST2, a process gas is supplied into the process container 12 from a selected gas source among a plurality of gas sources of the gas source group 40. [ The process gas may include a hydrogen gas and a nitrogen gas. The process gas used in step ST2 may be a process gas containing another gas such as an oxygen gas as long as it can etch the organic film. Further, in step ST2, the exhaust device 50 is operated, and the pressure in the processing container 12 is set to a predetermined pressure. In step ST2, high-frequency power from the first high-frequency power source 62 is supplied to the upper electrode 30, and high-frequency bias power from the second high-frequency power source 64 is supplied to the lower electrode LE.

Various conditions in step ST2 will be exemplified below.

Pressure in the processing vessel: 50 mTorr (6.65 Pa) to 200 mTorr (26.6 Pa)

ㆍ Process gas

N ₂ gas: 200 sccm to 400 sccm

H ₂ gas: 200 sccm to 400 sccm

ㆍ High-frequency power for plasma generation: 500W to 2000W

ㆍ High frequency bias power: 200W ~ 500W

In the process ST2, a plasma of the process 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 a portion of the entire region of the organic film OL exposed from the opening of the antireflection film AL is removed. That is, the pattern of the antireflection film AL is transferred to the organic film OL, a pattern for providing the opening MO is formed in the organic film OL, and a mask MK is generated from the organic film OL. The operation of each section of the plasma processing apparatus 10 in step ST2 described above can be controlled by the control section Cnt.

In one embodiment, step ST3 is executed after execution of step ST2. In the process 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 is slightly left on the second region R2. Therefore, in step ST3, the processing gas is supplied into the processing vessel 12 from the selected gas source among the plurality of gas sources of the gas source group 40. [ This process gas includes a fluorocarbon gas. Further, the process gas may further include a rare gas such as Ar gas. Further, the process gas may further include oxygen gas. In step ST3, the exhaust device 50 is operated to set the pressure in the processing container 12 to a predetermined pressure. In step ST3, the high-frequency power from the first high-frequency power supply 62 is supplied to the upper electrode 30 and the high-frequency bias power from the second high-frequency power supply 64 is supplied to the lower electrode LE.

In the process ST3, plasma of the process gas is generated, and the first region R1 is etched by the active species of the fluorocarbon in a 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 on the second region R2 at a predetermined film thickness at the end of the step ST3. As a result of the execution of this step ST3, as shown in Fig. 6, the upper opening UO is partially formed. The operation of each section of the plasma processing apparatus 10 described above in step ST3 can be controlled by the control section Cnt.

Here, in a step ST11 to be described later, a mode in which formation of deposits containing fluorocarbon on the surface of the wafer W including the first region R1 is superior to etching of the first region R1, that is, Is selected. On the other hand, in the step ST3, a mode in which the etching of the first region R1 is superior to the formation of the deposit, that is, a condition that becomes the etching mode is selected. Therefore, in one example, the fluorocarbon gas used in the step ST3 may include at least one of C ₄ F ₈ gas and CF ₄ gas. The fluorocarbon gas in this example has a fluorine atom number relative to the number of carbon atoms (i.e., the number of fluorine atoms / carbon atoms) relative to the ratio of the number of fluorine atoms to the number of carbon atoms in the fluorocarbon gas (That is, the number of fluorine atoms / the number of carbon atoms) is a high fluorocarbon gas. Further, in one example, in order to increase the degree of dissociation of the fluorocarbon gas, the RF power for plasma generation used in the process ST3 may be set to be higher than the RF power for plasma generation used in the process ST11. According to these examples, the etching mode can be realized. Further, in one example, the high-frequency bias power used in step ST3 may also be set to a higher power than the high-frequency bias power in step ST11. According to this example, the energy of the ions attracted to the wafer W can be increased, and the first region R1 can be etched at high speed.

Various conditions in step ST3 will be exemplified below.

Pressure in the processing vessel: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)

ㆍ Process 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

ㆍ High-frequency power for plasma generation: 500W to 2000W

ㆍ High frequency bias power: 500W ~ 2000W

In one embodiment, the next step ST4 is executed. In step ST4, a plasma of a process gas containing an oxygen-containing gas is generated in the process vessel 12. [ To this end, in process ST4, a process gas is supplied into the process container 12 from a selected gas source among a plurality of gas sources of the gas source group 40. [ The process gas may include, for example, oxygen gas as an oxygen-containing gas. Further, the process gas may further include an inert gas such as a rare gas (for example, Ar gas) or nitrogen gas. In step ST4, the exhaust device 50 is operated to set the pressure in the processing container 12 to a predetermined pressure. Further, in step ST4, the 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, an active species of oxygen is generated, and the opening MO of the mask MK is widened at the upper part by the active species of the oxygen. Specifically, as shown in Fig. 7, the upper shoulder portion of the mask MK for defining the upper portion of the opening MO is etched so as to exhibit a tapered shape. This makes it possible to reduce the amount of reduction in the width of the opening MO even if the deposit generated in the subsequent steps adheres to the surface defining the opening MO of the mask MK. The operation of each section of the plasma processing apparatus 10 described above in step ST4 can be controlled by the control section Cnt.

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

Various conditions in step ST4 are exemplified below.

Pressure in the processing vessel: 30 mTorr (3.99 Pa) to 200 mTorr (26.6 Pa)

ㆍ Process 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

ㆍ High frequency bias power: 0W ~ 200W

Then, in the method MT, the sequence SQ is repeatedly executed to etch the first region R1. Sequence SQ includes step ST11, step ST12, and step ST13 in this order.

In sequence SQ, firstly, step ST11 is executed. In step ST11, a plasma of the process gas is generated in the process container 12 containing the wafer W. To this end, in process ST11, a process gas is supplied into the processing vessel 12 from a gas source selected from a plurality of gas sources of the gas source group 40. [ This process gas includes a fluorocarbon gas. Further, the process gas may further include a rare gas such as Ar gas. Further, in step ST11, the exhaust device 50 is operated, and the pressure in the processing container 12 is set to a predetermined pressure. In step ST11, high-frequency power from the first high-frequency power supply 62 is supplied to the upper electrode 30. [ As a result, a plasma of a process gas containing 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 plasma processing apparatus 10 described above in step ST11 can be controlled by the control unit Cnt.

As described above, in step ST11, a condition to be the deposition mode is selected. For this reason, in one example, C ₄ F ₆ gas is used as the fluorocarbon gas.

Various conditions in step ST11 will be exemplified below.

Pressure in the processing vessel: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)

ㆍ Process 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

ㆍ High frequency bias power: 0W

In the method MT, the next step ST12 is executed. In step ST12, a plasma of a process gas containing an oxygen-containing gas and an inert gas is generated in the processing vessel 12. [ To this end, in process ST12, a process gas is supplied into the process container 12 from a gas source selected from a plurality of gas sources of the gas source group 40. [ In one example, the process gas includes oxygen gas as an oxygen-containing gas. Further, in one example, the process gas includes a rare gas called an Ar gas as an inert gas. The inert gas may be nitrogen gas. Further, in step ST12, the exhaust device 50 is operated, and the pressure in the processing container 12 is set to a predetermined pressure. In step ST12, high-frequency power from the first high-frequency power supply 62 is supplied to the upper electrode 30. [ In step ST12, 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 the deposit DP on the wafer W due to the active species of oxygen is appropriately reduced as shown in Fig. As a result, the opening MO and the upper opening UO are prevented from being obstructed by the excess sediment DP. Further, in the process gas used in the process ST12, the oxygen gas is diluted by the inert gas, so that the sediment DP can be prevented from being excessively removed. The operation of each section of the above-described plasma processing apparatus 10 in this step ST12 can be controlled by the control section Cnt.

Various conditions in step ST12 are exemplified below.

Pressure in the processing vessel: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)

ㆍ 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

ㆍ High frequency bias power: 0W

In one embodiment, step ST12 of each sequence, that is, one step ST12 is executed for 2 seconds or longer, and the sediment DP can be etched at a rate of 1 nm / sec or less in step ST12. To execute the above-described sequence using the plasma processing apparatus such as the plasma processing apparatus 10, it takes time to switch the gas for the transition between the steps ST11, ST12, and ST13. Therefore, considering the time required for stable discharge, step ST12 needs to be executed for 2 seconds or more. However, if the rate of etching of the deposit DP in such a time length period is too high, the deposit for protecting the second region R2 can be over-removed. Therefore, in step ST12, the deposit DP is etched at a rate of 1 nm / sec or less. Thus, the amount of the deposit DP formed on the wafer W can be appropriately adjusted. The rate of 1 nm / sec or less of the etching of the deposit DP in the step ST12 depends on the pressure in the processing vessel, the degree of dilution by the rare gas of oxygen in the processing gas, that is, the oxygen concentration and the high frequency Power can be achieved by selecting from the above-described conditions.

In the next step ST13, the first region R1 is etched. To this end, in step ST13, a process gas is supplied into the processing vessel 12 from a gas source selected from a plurality of gas sources of the gas source group 40. [ This process gas includes an inert gas. The inert gas may be, for example, a rare gas called Ar gas. Alternatively, the inert gas may be nitrogen gas. Further, in step ST13, the exhaust apparatus 50 is operated, and the pressure in the processing vessel 12 is set to a predetermined pressure. In step ST13, the high-frequency power from the first high-frequency power supply 62 is supplied to the upper electrode 30. [ In step ST13, high-frequency bias power from the second high-frequency power supply 64 is supplied to the lower electrode LE.

Various conditions in step ST13 will be exemplified below.

Pressure in the processing vessel: 10 mTorr (1.33 Pa) to 50 mTorr (6.65 Pa)

ㆍ Process gas

 Ar gas: 500 sccm to 1500 sccm

High-frequency power for plasma generation: 100 W to 500 W

ㆍ High frequency bias power: 20W ~ 300W

In step ST13, a plasma of an inert gas is generated, and ions are attracted to the wafer W. Then, the first region R1 is etched by the radical of the fluorocarbon 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 section of the plasma processing apparatus 10 in the step ST13 described above can be controlled by the control section Cnt.

In the method MT, the sequence SQ including the above-described steps ST11 to ST13 is repeated. Then, as shown in Fig. 11, with the repetition of the sequence SQ, the sediment DP is formed on the wafer W by the execution of the step ST11. Then, as shown in Fig. 12, by the execution of step ST12, the amount of the deposit DP is reduced. Then, as shown in Fig. 13, the first region R1 is further etched by the execution of the step ST13, and the depth of the lower opening LO is deepened. Further, with the repetition of the sequence SQ, as shown in Fig. 14, the sediment DP is formed on the wafer W by the execution of the step ST11. Then, as shown in Fig. 15, the amount of the deposit DP is reduced by the execution of the step ST12. Then, as shown in Fig. 16, the first region R1 is further etched by the execution of the process ST13, and the depth of the lower opening LO is further deepened. 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 judged whether or not the stop condition is satisfied in the process STa. The stop condition is determined to be satisfied when the sequence SQ is executed a predetermined number of times. When it is determined in step STa that the stop condition is not satisfied, the sequence SQ is executed from step ST11. On the other hand, in step STa, when it is determined 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 the sequence SQ (hereinafter, referred to as " first sequence ") executed in the period including the time when the second region R2 is exposed is larger than the sequence The condition for repetition of the sequence SQ may be set such that the first region R1 is less than the amount of etching in the 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 step ST11, the execution time length of step ST12, and the execution time length of step ST13 in the first sequence is the execution time length of step ST11 in the second sequence, , And the execution time length of the process 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, the execution time length of the process ST12 is selected from the time length in the range of 2 seconds to 5 seconds, The execution time length is selected from a time length ranging from 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, the execution time length of the process ST12 is selected from the time length in the range of 2 seconds to 10 seconds, The execution time length is selected from a time length ranging from 5 seconds to 20 seconds.

The active species of the fluorocarbon generated in the step ST11 is deposited on the second region R2 to protect the second region R2. However, when the first region R1 is etched and the second region R2 is exposed, the active region of the second region R2 Can be etched. Thus, in one embodiment, the first sequence is executed in the period in which the second region R2 is exposed. Thus, the deposit DP is formed on the wafer W while suppressing the etching amount, and the second region R2 is protected by the deposit DP. After this, a 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 second region R2 from being cut.

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

As shown in Fig. 14, after the execution of the first sequence and the second sequence, the amount of the deposit DP on the wafer W is considerably increased. As the amount of the deposit DP increases, the width of the opening MO, the width of the upper opening UO, and the width of the lower opening LO are narrowed by the deposit DP. Thereby, a phenomenon may occur in which the flow rate of ions reaching the deep portion of the lower opening LO is insufficient. However, since a relatively large high-frequency bias power is used in step ST13 of the third sequence, the energy of ions attracted to the wafer W can be increased. As a result, even if the lower opening LO is deep, it becomes possible to supply ions to the deep portion of the lower opening LO.

Hereinafter, an etching method according to another embodiment will be described. 17 is a flowchart showing an etching method according to another embodiment. Figs. 18 and 19 are cross-sectional views showing an object to be processed after the execution of step ST14 of the method shown in Fig. Fig. 18 shows the state of the cross section of the wafer after the step ST14 is performed on the wafer W shown in Fig. 10, and Fig. 19 shows the state of the cross section of the wafer after the step ST14 is performed on the wafer W shown in Fig. Respectively. 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 step as step ST12. The conditions described above with respect to the process of step ST12 may be employed as the conditions in the process of step ST14.

Ions are attracted to the wafer W in step ST13 as described above. As a result, the substance constituting the deposit DP is released from the wafer W, the substance is attached again to the wafer W, and as shown in Figs. 10 and 13, the deposit MO . This deposit DP may occasionally occlude the opening MO and the lower opening LO. In the method MT2, the wafer W shown in Figs. 10 and 13 is exposed to the active species of oxygen in the same manner as the step ST12 by the execution of the step ST14. As a result, the sediment DP (see Figs. 10 and 13) for narrowing the widths of the opening MO and the lower opening LO can be reduced as shown in Figs. 18 and 19, and the clogging of the opening MO and the lower opening LO can be prevented It is possible to more reliably prevent it.

Various embodiments have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in the implementation of the method MT, although the high-frequency power for plasma generation is supplied to the upper electrode 30, the high-frequency power may be supplied to the lower electrode LE. The method MT may be implemented by using a plasma processing apparatus other than the plasma processing apparatus 10. Specifically, it is possible to perform the method MT using an arbitrary plasma processing apparatus, such as an inductively coupled plasma processing apparatus or a plasma processing apparatus for generating plasma by a surface wave called a microwave.

Also, the order of execution 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 step ST12 may be executed after the execution of the step ST13.

10: Plasma processing device
12: Processing vessel
30: upper electrode
PD: Mounting table
LE: Lower electrode
ESC: electrostatic chuck
40: gas source group
42: valve group
44: Flow controller group
50: Exhaust system
62: first high frequency power source
64: Second high frequency power source
Cnt:
W: Wafer
R1: first region
R2: second region
OL: organic film
AL: Silicon-containing antireflection film
MK: Mask
DP: sediment

Claims (4)

A method for selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride by a plasma treatment on the object to be processed,
Wherein the object to be processed has the second region for partitioning the concave portion, the first region filled in the concave portion and covering the second region, and the mask provided on the first region,
The method comprises:
A first step of producing a plasma of a process gas containing a fluorocarbon gas in a process container accommodating the process subject, wherein the process comprises the steps of: forming a deposit containing fluorocarbon on the process subject; ,
A second step of generating a plasma of a process gas containing an oxygen-containing gas and an inert gas in the process container accommodating the object to be processed,
A third step of etching the first region by the radical of the fluorocarbon contained in the deposit
/ RTI >
A sequence including the first process, the second process, and the third process is repeatedly executed
Way.
The method according to claim 1,
The mask is made of an organic material,
On the mask, a silicon-containing antireflection film is provided,
A fourth step of producing a plasma of a process gas containing a fluorocarbon gas in the processing vessel, the fourth step of etching the first region until immediately before the second region is exposed;
A fifth step of generating a plasma of a process gas containing an oxygen-containing gas in the process vessel
Further comprising:
After the execution of the fourth step and the fifth step, the sequence is executed
Way.
3. The method according to claim 1 or 2,
Wherein the second step is performed for at least 2 seconds and the deposits are etched at a rate of 1 nm / second or less in the second step.
4. The method according to any one of claims 1 to 3,
In the sequence, the second step is executed between the first step and the third step,
The sequence further includes another process for producing a plasma of a process gas containing an oxygen-containing gas and an inert gas in a process container accommodating the object to be processed
Way.

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