Etching method and plasma processing apparatus

Abstract

The present disclosure provides an etching method and a plasma processing apparatus that suppresses abnormality in the shape of a recess formed in a silicon-containing film and advances etching of the bottom of the recess. The disclosed etching method includes a process (a) of preparing a substrate having a silicon-containing film including a silicon oxide film. The substrate is placed on a substrate support provided in a chamber. The etching method also includes a process (b) of supplying a processing gas into the chamber. The processing gas contains a tungsten hexafluoride gas, a carbon-and-fluorine-containing gas, and an oxygen-containing gas. The etching method also includes a process (c) of generating plasma from the processing gas to etch the silicon-containing film. The process (c) includes periodically applying a negative direct current voltage to the substrate support.

Description

Technical Field

[0001] The exemplary embodiments of this disclosure relate to an etching method and a plasma processing apparatus. Background Technology

[0002] Plasma etching is performed to form recesses in a silicon-containing film on a substrate. In plasma etching, a technique is proposed that involves simultaneously forming a conductive layer on the surface of the substrate and etching the silicon-containing film to suppress abnormal shapes of the recesses. Patent Document 1 discloses such a technique.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 9-50984 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a technique for suppressing shape anomalies in recesses formed on silicon-containing films and for advancing etching at the bottom of the recesses.

[0008] Solution for solving the problem

[0009] An exemplary embodiment provides an etching method. The etching method includes a step (a) of preparing a substrate having a silicon-containing film, said silicon-containing film comprising a silicon oxide film. The substrate is placed on a substrate support disposed within a chamber. The etching method further includes a step (b) of supplying a process gas into the chamber. The process gas comprises tungsten hexafluoride gas, a carbon- and fluorine-containing gas, and an oxygen-containing gas. The etching method further includes a step (c) of etching the silicon-containing film by generating plasma from the process gas. Step (c) includes periodically applying a negative DC voltage to the substrate support.

[0010] The effects of the invention

[0011] According to an exemplary embodiment, it is possible to suppress shape abnormalities in the recesses formed on the silicon-containing film and to allow etching progress at the bottom of the recesses. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating an etch method according to an exemplary implementation.

[0013] Figure 2 This is a partial magnified cross-sectional view of an example substrate.

[0014] Figure 3 This is a partially enlarged cross-sectional view of the substrate in other examples.

[0015] Figure 4 Through Figure 1 A partially enlarged cross-sectional view of a substrate during the STc process of the etching method shown.

[0016] Figure 5 Is with Figure 1 The timing diagram associated with process STc2 in the etching method shown.

[0017] Figure 6 Is execution Figure 1 A partially enlarged cross-sectional view of an example substrate after the etching method shown.

[0018] Figure 7 This is a partially enlarged cross-sectional view of the substrate in other examples.

[0019] Figure 8 This is a flowchart of an etching method involved in other exemplary embodiments.

[0020] Figure 9 This is a diagram that schematically illustrates a plasma processing apparatus according to an exemplary embodiment.

[0021] Figure 10 It is a cross-sectional view that schematically represents a portion of the sample substrate after it has been etched in the experiment.

[0022] Figure 11 (a) is a graph showing the atomic fractions of silicon and tungsten at region RS obtained experimentally. Figure 11 (b) is a graph showing the atomic fractions of silicon and tungsten at region RB obtained through experiments. Detailed Implementation

[0023] The following describes various exemplary implementation methods.

[0024] An exemplary embodiment provides an etching method. The etching method includes a step (a) of preparing a substrate having a silicon-containing film, said silicon-containing film comprising a silicon oxide film. The substrate is placed on a substrate support disposed within a chamber. The etching method further includes a step (b) of supplying a process gas into the chamber. The process gas comprises tungsten hexafluoride gas, a carbon- and fluorine-containing gas, and an oxygen-containing gas. The etching method further includes a step (c) of etching the silicon-containing film by generating plasma from the process gas. Step (c) includes periodically applying a negative DC voltage to the substrate support.

[0025] In one exemplary embodiment, step (c) may further include replacing a portion of the silicon atoms in the silicon-containing film with tungsten atoms at the bottom surface of the recess formed by etching in the silicon-containing film. Alternatively, step (c) may further include etching the silicon-containing film after the portion of silicon atoms has been replaced with tungsten atoms.

[0026] In one exemplary embodiment, step (c) may also include applying a negative DC voltage to the upper electrode disposed above the substrate support when no negative DC voltage is applied to the substrate support. In this embodiment, a relatively large number of secondary electrons emitted from the upper electrode can be supplied to the substrate when no negative DC voltage is applied to the substrate support. Therefore, the charge at the bottom of the recess can be neutralized.

[0027] In one exemplary embodiment, it is also possible that when a negative DC voltage is applied to the substrate support in step (c), a negative DC voltage is not applied to the upper electrode. Alternatively, it is also possible that when a negative DC voltage is applied to the substrate support, the absolute value of the negative DC voltage applied to the upper electrode is smaller than the absolute value of the negative DC voltage applied to the upper electrode when no negative DC voltage is applied to the substrate support.

[0028] In one exemplary embodiment, the pressure in the chamber during step (c) may also be set to less than 1.333 Pa.

[0029] In one exemplary embodiment, the flow rate of tungsten hexafluoride gas in the process gas may be less than 5% by volume relative to the flow rate of the process gas.

[0030] In one exemplary embodiment, the processing gas may also include nitrogen trifluoride gas.

[0031] In one exemplary embodiment, the flow rate of nitrogen trifluoride gas in the process gas may be greater than the flow rate of tungsten hexafluoride gas in the process gas.

[0032] In one exemplary embodiment, the silicon-containing film may also include a silicon oxide film. Alternatively, the processing gas may include a fluorocarbon gas as a carbon and fluorine-containing gas. Alternatively, the silicon-containing film may also include a silicon nitride film. Alternatively, in step (c), a tungsten-containing film may be formed on the sidewalls of the silicon nitride film by etching. Alternatively, the silicon-containing film may also include a polycrystalline silicon film.

[0033] In one exemplary embodiment, the silicon-containing film may also include a silicon nitride film. Alternatively, the processing gas may comprise a hydrofluorocarbon gas as a carbon and fluorine-containing gas.

[0034] In one exemplary embodiment, the silicon-containing film may also comprise a laminated film having a silicon oxide film and a silicon nitride film. Alternatively, step (c) may include etching the silicon nitride film at a bias frequency set to a first frequency, said bias frequency being the reciprocal of the time interval for applying a negative DC voltage to the substrate support. Alternatively, step (c) may include etching the silicon oxide film at a bias frequency set to a second frequency greater than the first frequency.

[0035] In one exemplary embodiment, the substrate may also have a base region or an etch stop layer. Alternatively, the etching method may further include a step of stopping the supply of tungsten hexafluoride gas in the process gas during the period when the base region or etch stop layer is exposed. Alternatively, the etching method may further include a step of etching the silicon-containing film using plasma generated from a gas other than tungsten hexafluoride contained in the process gas.

[0036] Other exemplary embodiments of the etching method include a step (a) of preparing a substrate having a silicon-containing film, said silicon-containing film comprising a silicon oxide film. The substrate is placed on a substrate support disposed within a chamber. The etching method further includes a step (b) of supplying a processing gas comprising tungsten hexafluoride gas, a carbon- and fluorine-containing gas, and an oxygen-containing gas into the chamber. The etching method further includes a step (c) of etching the silicon-containing film by generating plasma from said processing gas. Step (c) includes replacing a portion of silicon atoms in the silicon-containing film with tungsten atoms at the bottom surface of a recess formed in the silicon-containing film by etching. Step (c) includes electrically biasing the substrate to remove the silicon-containing film after a portion of the silicon atoms have been replaced by tungsten atoms.

[0037] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a gas supply unit, a plasma generation unit, and a DC power supply. The substrate support includes a lower electrode and is disposed within the chamber. The gas supply unit is configured to supply a processing gas comprising tungsten hexafluoride gas, a carbon- and fluorine-containing gas, and an oxygen-containing gas into the chamber. The plasma generation unit is configured to generate plasma from the processing gas within the chamber. The DC power supply is configured to periodically apply a negative DC voltage to the substrate support.

[0038] The following description, with reference to the accompanying drawings, details various exemplary embodiments. Furthermore, the same or equivalent parts are labeled with the same reference numerals in each drawing.

[0039] Figure 1 This is a flowchart illustrating an exemplary embodiment of an etching method. (Performance) Figure 1 The etching method shown (hereinafter referred to as "Method MT") is used to etch a silicon-containing film on a substrate to form a recess in the silicon-containing film.

[0040] Figure 2 This is a partial magnified cross-sectional view of an example substrate. Figure 3 This is a partially enlarged cross-sectional view of another example substrate. The MT method can be applied to... Figure 2 or Figure 3 The substrate W shown is an example. Figure 2 and Figure 3 As shown, the substrate W has a silicon-containing film SF. The substrate W may also have a mask MK and a substrate region UR. The silicon-containing film SF is disposed on the substrate region UR. The mask MK is disposed on the silicon-containing film SF. The mask MK is formed of an organic material such as polycrystalline silicon or amorphous carbon. The mask MK has a pattern to be transferred to the silicon-containing film SF by etching. That is, the mask MK provides more than one opening.

[0041] The silicon-containing film SF is formed from at least one silicon-containing material. The silicon-containing film SF may include a silicon oxide film OX. The silicon-containing film SF can be formed from a single layer of silicon oxide film. The silicon-containing film SF can also be formed from a multilayer film comprising one or more silicon oxide films OX and one or more silicon nitride films SN. Figure 3 As shown, the silicon-containing film SF can also include a stacked film having a silicon oxide film OX and a silicon nitride film SN. The silicon nitride film SN can be disposed on the silicon oxide film OX. The silicon-containing film SF can also be formed from a multilayer film including one or more silicon oxide films and one or more polycrystalline silicon films.

[0042] like Figure 1 As shown, method MT begins with step Sta. In step Sta, substrate W is prepared. In step Sta, substrate W is placed on a substrate support disposed within the chamber of the plasma processing apparatus.

[0043] In the subsequent step STb, a processing gas is supplied to the chamber of the plasma processing apparatus. The processing gas includes tungsten hexafluoride gas (WF6 gas), carbon- and fluorine-containing gases, and oxygen-containing gases. The processing gas may also include nitrogen trifluoride gas (NF3 gas). It is permissible that the flow rate of nitrogen trifluoride gas in the processing gas supplied to the chamber is greater than the flow rate of tungsten hexafluoride gas in the processing gas. It is permissible that the flow rate of WF6 gas in the processing gas supplied to the chamber is 5% by volume or less.

[0044] When the silicon-containing membrane SF includes a silicon oxide membrane OX, the carbon- and fluorine-containing gas in the process gas includes a fluorocarbon gas. The fluorocarbon gas may include one or more of C4F6, C4F8, C3F8, and CF4. When the silicon-containing membrane SF includes a silicon nitride membrane SN, the carbon- and fluorine-containing gas in the process gas may include a hydrofluorocarbon. The hydrofluorocarbon may include one or more of CH3F, CH2F2, and CHF3. The oxygen-containing gas in the process gas may include one or more of O2, CO, and CO2.

[0045] Process STc is performed during the supply of process gas into the chamber in process STb. Process STc includes processes STc1 and STc2. In process STc1, plasma is generated in the chamber from the process gas. In process STc, the silicon-containing film SF is etched using chemical species derived from the plasma. Figure 4 Through Figure 1 A partially enlarged cross-sectional view of a substrate during the STc process of the etching method shown. Figure 4 As shown, a recess RC is formed in a silicon-containing film SF by etching in process STc. In process STc, at the bottom surface of the recess RC, a portion of the silicon atoms in the silicon-containing film SF are replaced with tungsten atoms supplied from plasma.

[0046] In cases where the silicon-containing film SF includes a silicon nitride film SN, in process STc, a tungsten-containing film WF is formed on the sidewall of the silicon nitride film SN that defines the recess RC. In process STc, the tungsten-containing film WF may be formed on the surface of the mask MK.

[0047] Process STc2 is performed while the plasma generated in process STc1 is present in the chamber. In process STc2, a portion of the silicon-containing film SF, after which silicon atoms have been replaced by tungsten atoms, is etched or removed. In process STc2, the substrate W is electrically biased. Therefore, in process STc2, the substrate support is electrically biased EB. Alternatively, the lower electrode within the substrate support may be electrically biased EB.

[0048] In one embodiment, the electrical bias EB is a voltage generated by waveform shaping of a DC voltage produced by a DC power supply using a waveform generator. The voltage as the electrical bias EB can have a rectangular pulse waveform, a triangular pulse waveform, or any arbitrary waveform. The voltage as the electrical bias EB is periodically applied to the substrate support. As long as the potential of the substrate W is set to provide a potential difference between the plasma and the substrate W to attract ions to the substrate W, the polarity of the voltage as the electrical bias EB can be negative or positive.

[0049] Figure 5 Is with Figure 1 The timing diagram associated with step STc2 in the etching method shown. In one embodiment, as... Figure 5 As shown, in process STc2, a negative DC voltage is periodically applied to the substrate support as an electrical bias EB, with a period CY (time interval). The period CY includes a period PA and a period PB. During period PA, a negative DC voltage is applied to the substrate support. During period PB, the application of the negative DC voltage to the substrate support is stopped. The absolute value of the negative DC voltage applied to the substrate support during period PA can be 1kV or more and 20kV or less. The proportion of period PA in period CY, i.e., the duty cycle of the negative DC voltage periodically applied to the substrate support in process STc, can be 5% or more and 40% or less. This duty cycle can also be 10% or more and 30% or less. Furthermore, the bias frequency can be 100kHz or more and 1MHz or less, where the bias frequency is the frequency of the defined period CY, i.e., the reciprocal of the time interval for applying the negative DC voltage to the substrate support. The bias frequency can also be 300kHz or more and 800kHz or less. The bias frequency can also be 500kHz or less. Furthermore, the duration of period CY is the reciprocal of the bias frequency of the specified period CY. Depending on the level, duty cycle, and frequency range of the negative DC voltage applied to the substrate support in process STc, ions with sufficient energy can be supplied to the bottom of the recess RC to suppress the formation of a tungsten-containing film WF at the bottom of the recess RC.

[0050] Figure 6 Is execution Figure 1 A partially enlarged cross-sectional view of an example substrate after the etching method shown. Figure 6 As shown, in process STc, the silicon-containing film SF can be etched until the recess RC reaches the surface of the substrate region UR. When process STc is completed, method MT ends.

[0051] In method MT, at the bottom surface where the recess RC is defined, a portion of the silicon atoms in the silicon-containing film SF are replaced with tungsten. Tungsten has a larger atomic weight than silicon, thus making the portion of the silicon-containing film SF where the silicon atoms are replaced by tungsten chemically unstable. Furthermore, fluoride ions from the plasma are easily electroattracted to this portion. Additionally, in the case where the silicon-containing film SF includes a silicon oxide film OX, the binding energy of tungsten with oxygen is lower than that of silicon with oxygen, making this portion easier to etch. Therefore, according to method MT, a high etching rate for the silicon-containing film SF can be obtained. Furthermore, due to the high etching rate of the silicon-containing film SF, the time the sidewalls of the silicon-containing film SF are exposed to chemical species from the plasma is shortened. As a result, the curvature of the silicon-containing film SF, such as the silicon oxide film OX, is suppressed.

[0052] In one embodiment, the plasma processing apparatus used in method MT can be a capacitively coupled plasma processing apparatus. That is, the plasma processing apparatus may also include an upper electrode. The upper electrode is disposed above the substrate support. In step STc, other electrical bias DCS may also be applied to the upper electrode. Specifically, such as... Figure 5 As shown, in process STc, during period CY, PB applies a negative DC voltage to the upper electrode as an electrical bias DCS. That is, when no negative DC voltage is applied to the substrate support in process STc, a negative DC voltage is applied to the upper electrode. In this embodiment, a relatively large number of secondary electrons emitted from the upper electrode can be supplied to the substrate W. Therefore, the charge at the bottom of the recess RC can be neutralized. Furthermore, during period PA, the application of the negative DC voltage to the upper electrode can be stopped. Alternatively, the absolute value of the negative DC voltage applied to the upper electrode during period PA can be smaller than the absolute value of the negative DC voltage applied to the upper electrode during period PB.

[0053] In one embodiment, during process STc, the pressure within the chamber can be set to a low pressure of less than 10 mTorr (1.333 Pa). In this case, excessive dissociation of carbon- and fluorine-containing gases, such as fluorocarbon gases, is suppressed. As a result, excessive deposition of carbonaceous material on the substrate W is suppressed. Furthermore, it suppresses the arc-shaped bending of the silicon oxide film OX caused by ions bouncing back after colliding with the carbonaceous material, which is deposited on the sidewalls defining the recesses RC.

[0054] Alternatively, during process STc, the temperature of the substrate support can be set to a temperature above 0°C and below 120°C. When the substrate support temperature in process STc is below 0°C, the adhesion coefficient of the deposit to the mask MK is high, which may cause blockage due to deposits on the mask MK, resulting in etching defects. Conversely, when the substrate support temperature in process STc is above 120°C, the adhesion coefficient of the deposit to the mask MK is low, which may result in excessive deposits in the recess RC, also leading to etching defects.

[0055] Furthermore, as mentioned above, when the processing gas also contains nitrogen trifluoride gas, the amount of carbonaceous material deposited on the upper part of the mask MK can be adjusted. As a result, it is possible to prevent the opening of the mask MK from shrinking or becoming blocked.

[0056] Additionally, as described above, in one embodiment, the flow rate of nitrogen trifluoride gas in the processing gas supplied to the chamber may be greater than the flow rate of tungsten hexafluoride gas in the processing gas relative to the flow rate of the processing gas. In this case, excessive deposition of tungsten-containing material on the substrate W is suppressed.

[0057] Furthermore, as described above, in one embodiment, the flow rate of tungsten hexafluoride gas in the processing gas supplied to the chamber can be 5% by volume or less relative to the flow rate of the processing gas. In this case, excessive deposition of tungsten-containing material on the bottom surface of the recess RC is suppressed.

[0058] In one embodiment, process STc may include etching a silicon nitride film SN at a bias frequency set to a first frequency, and etching a silicon oxide film OX at a bias frequency set to a second frequency. The first frequency can be 200 kHz or higher and 300 kHz or lower. The second frequency is higher than the first frequency. When the bias frequency is set to the first frequency, the main chemical species that facilitate etching are free radicals. On the other hand, when the bias frequency is set to the second frequency, the main chemical species that facilitate etching are ions. Therefore, in this case, the silicon nitride film SN can be etched using free radicals from the plasma. Additionally, the silicon oxide film OX can be etched using ions from the plasma.

[0059] Below, refer to Figure 7 . Figure 7 These are magnified cross-sectional views of substrates from other examples. The MT method can also be applied... Figure 7 The substrate W shown is... and... Figure 2 or Figure 3 The substrate W shown is the same. Figure 7 The substrate W shown has a substrate region UR, a silicon-containing film SF, and a mask MK. The mask MK has multiple openings. Figure 7 The substrate W shown also has multiple etch stop layers ES. The multiple etch stop layers ES are respectively disposed within the silicon-containing film SF between corresponding openings in multiple openings of the mask MK and the substrate region UR. The positions of the multiple etch stop layers ES in the thickness direction within the silicon-containing film SF are different from each other. The multiple etch stop layers ES are formed, for example, of tungsten. In the... Figure 7 When the substrate W is applied using method MT, the etching of the silicon-containing film SF of process STc can be stopped at multiple etch stop layers ES.

[0060] Below, refer to Figure 8 . Figure 8 This is a flowchart of an etching method involved in other exemplary embodiments. Figure 8The method MTB shown, like method MT, includes steps STa, STb, and STc. Method MTB also includes steps STd and STe. Steps STd and STe are performed after step STc.

[0061] Process STd begins before the recess RC formed by etching in process STc reaches the substrate region UR or the etch stop layer ES. Process STd is also performed during the period when the substrate region UR or the etch stop layer ES is exposed. In process STd, the supply of tungsten hexafluoride gas, one of all gases contained in the process gas supplied to the chamber from process STb, is stopped. After process STd, other gases contained in the process gas supplied to the chamber from process STb can continue to be supplied to the chamber.

[0062] STe is performed after step STd. In step STe, the supply of tungsten hexafluoride gas is stopped, and other gases contained in the process gas are supplied to the chamber. In step Ste, plasma is generated in the chamber by the gases other than tungsten hexafluoride contained in the process gas. In step Ste, the silicon-containing film SF is etched by the chemical species from the plasma. Furthermore, in step STe, plasma is generated in the same manner as in step STc. Additionally, in step STe, an electrical bias EB is periodically applied to the substrate support in the same manner as in step STc. According to this method MTB, the deposition of tungsten-containing material on the substrate region UR or the etch stop layer ES is suppressed.

[0063] The plasma processing apparatus that can be used to execute method MT will now be described. Figure 9 This is a diagram that schematically illustrates a plasma processing apparatus according to an exemplary embodiment. For method MT and method MTB, it is possible to use... Figure 9 The plasma processing device 1 shown is a capacitively coupled plasma processing device.

[0064] The plasma processing apparatus 1 includes a chamber 10. The chamber 10 provides an internal space 10s therein. The central axis of the chamber 10 is an axis AX extending vertically. In one embodiment, the chamber 10 includes a chamber body 12. The chamber body 12 has a generally cylindrical shape. The internal space 10s is provided within the chamber body 12. The chamber body 12 is made of, for example, aluminum. The chamber body 12 is electrically grounded. A corrosion-resistant film is provided on the inner wall surface of the chamber body 12. The corrosion-resistant film can be a film formed of ceramics such as alumina or yttrium oxide.

[0065] The chamber body 12 has a passage 12p on its side wall. When a substrate W is transferred between the internal space 10s and the outside of the chamber 10, the substrate W passes through the passage 12p. The passage 12p can be opened and closed by a gate valve 12g. The gate valve 12g is provided along the side wall of the chamber body 12.

[0066] The plasma processing apparatus 1 also includes a substrate support 16. The substrate support 16 is configured to support a substrate W within the chamber 10. The substrate W can have a generally disc-shaped form. The substrate support 16 can be supported by a support body 15. The support body 15 extends upward from the bottom of the chamber body 12. The support body 15 has a generally cylindrical shape. The support body 15 is formed of an insulating material such as quartz.

[0067] The substrate support 16 includes a base 18. The substrate support 16 may also include an electrostatic chuck 20. Additionally, the substrate support 16 may also include an electrode plate 19. The electrode plate 19 is formed of a conductive material such as aluminum. The electrode plate 19 has a generally disk-shaped form with its central axis AX. The base 18 is disposed on the electrode plate 19. The base 18 is formed of a conductive material such as aluminum. The base 18 has a generally disk-shaped form with its central axis AX. The base 18 is electrically connected to the electrode plate 19.

[0068] The base 18 provides a flow path 18f within it. Flow path 18f is for a heat exchange medium (e.g., refrigerant). Flow path 18f receives the heat exchange medium from a supply device (e.g., a cooling unit) via piping 23a. This supply device is located outside the chamber 10. The heat exchange medium supplied to flow path 18f flows through flow path 18f and then returns to the supply device via piping 23b. The heat exchange medium supply device constitutes the temperature regulation mechanism of the plasma processing apparatus 1.

[0069] An electrostatic chuck 20 is disposed on a base 18. A substrate W is placed on the upper surface of the electrostatic chuck 20. The electrostatic chuck 20 has a body and chuck electrodes. The body of the electrostatic chuck 20 is formed of a dielectric. The electrostatic chuck 20 and its body are each generally disk-shaped, and their central axis is axis AX. The chuck electrodes are films formed of conductors and are disposed within the body of the electrostatic chuck 20. The chuck electrodes are connected to a DC power supply via a switch. When a voltage from the DC power supply is applied to the chuck electrodes, an electrostatic attraction is generated between the electrostatic chuck 20 and the substrate W. By the generated electrostatic attraction, the substrate W is attracted to the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0070] The substrate support 16 may also support an edge ring ER disposed thereon. The edge ring ER may be formed of silicon, silicon carbide, or quartz. The substrate W is disposed on the electrostatic chuck 20 and within the area surrounded by the edge ring ER.

[0071] The plasma processing apparatus 1 may also include a gas supply line 25. The gas supply line 25 supplies heat transfer gas (e.g., He gas) from the gas supply mechanism to the gap between the upper surface of the electrostatic chuck 20 and the back (lower surface) of the substrate W.

[0072] The plasma processing apparatus 1 may also include a cylindrical portion 28 and an insulating portion 29. The cylindrical portion 28 extends upward from the bottom of the chamber body 12. The cylindrical portion 28 extends along the outer periphery of the support 15. The cylindrical portion 28 is formed of a conductive material and has a generally cylindrical shape. The cylindrical portion 28 is electrically grounded. The insulating portion 29 is disposed on the cylindrical portion 28. The insulating portion 29 is formed of an insulating material. The insulating portion 29 is formed, for example, of ceramic such as quartz. The insulating portion 29 has a generally cylindrical shape. The insulating portion 29 extends along the outer periphery of the electrode plate 19, the outer periphery of the base 18, and the outer periphery of the electrostatic chuck 20.

[0073] The plasma processing apparatus 1 also includes an upper electrode 30. The upper electrode 30 is disposed above the substrate support 16. The upper electrode 30 is supported on the upper part of the chamber body 12 via a member 32. The member 32 is formed of an insulating material. The upper electrode 30 and the member 32 close the upper opening of the chamber body 12.

[0074] The upper electrode 30 may also include a top plate 34 and a support 36. The lower surface of the top plate 34 is the lower surface on the side adjacent to the internal space 10s, defining the internal space 10s. The top plate 34 can be formed of a low-resistance conductor or semiconductor with low Joule heating. In one embodiment, the top plate 34 is formed of silicon. The top plate 34 is provided with a plurality of gas holes 34a. The plurality of gas holes 34a penetrate the top plate 34 along the thickness direction of the top plate 34.

[0075] The support body 36 supports the top plate 34 in a removable manner. The support body 36 is formed of a conductive material such as aluminum. The support body 36 provides a gas diffusion chamber 36a within itself. The support body 36 also provides a plurality of gas holes 36b. The plurality of gas holes 36b extend downward from the gas diffusion chamber 36a. The plurality of gas holes 36b communicate with the plurality of gas holes 34a respectively. The support body 36 also provides a gas inlet 36c. The gas inlet 36c is connected to the gas diffusion chamber 36a. The gas inlet 36c is connected to a gas supply pipe 38.

[0076] Gas supply pipe 38 is connected to gas source group 40 via valve group 41, flow controller group 42, and valve group 43. Gas source group 40, valve group 41, flow controller group 42, and valve group 43 constitute gas supply unit GS. Gas source group 40 includes multiple gas sources. The multiple gas sources of gas source group 40 include gas sources of various gases used in method MT or method MTB. Valve group 41 and valve group 43 each include multiple on / off valves. Flow controller group 42 includes multiple flow controllers. The multiple flow controllers of flow controller group 42 are either mass flow controllers or pressure-controlled flow controllers. The multiple gas sources of gas source group 40 are connected to gas supply pipe 38 via corresponding on / off valves in valve group 41, corresponding flow controllers in flow controller group 42, and corresponding on / off valves in valve group 43, respectively.

[0077] The plasma processing apparatus 1 may also include a shield 46. The shield 46 is installed along the inner wall of the chamber body 12 in a removable manner. The shield 46 is used to prevent plasma processing byproducts from adhering to the chamber body 12. The shield 46 is constructed, for example, by forming a corrosion-resistant film on the surface of a component made of aluminum. The corrosion-resistant film can be a film formed of ceramics such as yttrium oxide.

[0078] The plasma processing apparatus 1 may also include a baffle member 48. The baffle member 48 is disposed between a member (e.g., cylindrical portion 28) surrounding the substrate support 16 and a shield 46. The baffle member 48 is constructed, for example, by forming a corrosion-resistant film on the surface of a member made of aluminum. The corrosion-resistant film can be a film formed of ceramic such as yttrium oxide. The baffle member 48 provides multiple through holes. An exhaust port is provided below the baffle member 48 and at the bottom of the chamber body 12. The exhaust port is connected to an exhaust device 50 via an exhaust pipe 52. The exhaust device 50 includes a pressure regulating valve and a vacuum pump such as a turbomolecular pump.

[0079] The plasma processing apparatus 1 also includes a high-frequency power supply 61 and a bias power supply 62. The high-frequency power supply 61 is configured to generate high-frequency electricity (hereinafter referred to as "high-frequency power HF"). The high-frequency power HF has a frequency suitable for plasma generation. The frequency of the high-frequency power HF is, for example, 27 MHz or higher and 100 MHz or lower. The high-frequency power supply 61 is connected to an electrode within a substrate support 16 via a matching adapter 61m. The matching adapter 61m has circuitry for matching the impedance of the load side of the high-frequency power supply 61 to the output impedance of the high-frequency power supply 61. In one embodiment, the high-frequency power supply 61 constitutes a plasma generation unit. The electrode within the substrate support 16 connected to the high-frequency power supply 61 may also be a base 18. In this case, the base 18 constitutes a lower electrode. The electrode within the substrate support 16 connected to the high-frequency power supply 61 may also be an electrode disposed within an electrostatic chuck 20. Furthermore, the high-frequency power supply 61 may also be connected to an upper electrode 30 via the matching adapter 61m.

[0080] The bias power supply 62 is configured to periodically apply an electrical bias EB to the substrate support 16. As described above, the electrical bias EB is a voltage generated by waveform shaping of a DC voltage generated by a DC power supply using a waveform generator. The voltage as the electrical bias EB can have a rectangular pulse waveform, a triangular pulse waveform, or any waveform. As long as the potential of the substrate W is set to provide a potential difference between the plasma and the substrate W to attract ions to the substrate W, the polarity of the voltage as the electrical bias EB can be negative or positive. Furthermore, the electrode within the substrate support 16 to which the electrical bias EB is applied by the bias power supply 62 can also be a base 18. In this case, the base 18 constitutes the lower electrode. The electrode within the substrate support 16 to which the electrical bias EB is applied by the bias power supply 62 can also be an electrode provided in the electrostatic chuck 20.

[0081] In one embodiment, as described above, the bias power supply 62 is configured to periodically apply a negative DC voltage to the substrate support 16 as an electrical bias EB during step STc2 of method MT. As described above, during period CY, PA applies a negative DC voltage from the bias power supply 62 to the substrate support 16. During period PB of period CY, the application of the negative DC voltage from the bias power supply 62 to the substrate support 16 is stopped.

[0082] In one embodiment, the plasma processing apparatus 1 may also include a DC power supply 70. The DC power supply 70 is configured to provide the aforementioned electrical bias DCS to the upper electrode 30. That is, the DC power supply 70 is configured to periodically apply a negative DC voltage to the upper electrode 30 as the electrical bias DCS. As described above, during the period CY, PB applies a negative DC voltage from the DC power supply 70 to the upper electrode 30. During the period CY, PA, the application of the negative DC voltage from the DC power supply 70 to the upper electrode 30 may be stopped. Alternatively, the absolute value of the negative DC voltage applied to the upper electrode during PA may be smaller than the absolute value of the negative DC voltage applied to the upper electrode during PB.

[0083] The plasma processing apparatus 1 may also include a control unit 80. The control unit 80 is a computer equipped with a processor, storage device, input device, display device, etc., and is used to control each part of the plasma processing apparatus 1. Specifically, the control unit 80 executes a control program stored in the storage device and controls each part of the plasma processing apparatus 1 based on process data stored in the storage device. Through the control of the control unit 80, the process specified by the process data is executed in the plasma processing apparatus 1. Method MT and method MTB can be executed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 through the control unit 80.

[0084] When using plasma processing apparatus 1 to apply method MT or method MTB to substrate W, in step STa, substrate W is placed on substrate support 16. In subsequent step STb, control unit 80 controls gas supply unit GS to supply the aforementioned processing gas into chamber 10. In subsequent step STc, control unit 80 controls exhaust device 50 to set the pressure inside chamber 10 to a specified pressure. Additionally, in step STc, control unit 80 controls plasma generation unit to generate plasma from the processing gas inside chamber 10. Specifically, control unit 80 controls high-frequency power supply 61 to supply high-frequency power HF. Furthermore, in step STc, control unit 80 controls bias power supply 62 to periodically apply electrical bias EB to substrate support 16. In one embodiment, control unit 80 controls DC power supply 70 in step STc to periodically apply a negative DC voltage to upper electrode 30 as the aforementioned electrical bias DCS.

[0085] When using plasma processing apparatus 1 to apply method MTB to substrate W, in process STd, control unit 80 controls gas supply unit GS to stop the supply of tungsten hexafluoride gas contained in the processing gas supplied to the chamber from process STb. In process STe, control unit 80 controls plasma generation unit to generate plasma from gases other than tungsten hexafluoride contained in the processing gas to further etch the silicon-containing film SF. Specifically, control unit 80 controls high-frequency power supply 61 to supply high-frequency power HF. In addition, in process STe, control unit 80 controls bias power supply 62 to periodically apply electrical bias EB to substrate support 16.

[0086] The above describes various exemplary embodiments, but the implementation is not limited to these exemplary embodiments. Various additions, omissions, substitutions, and modifications can be made. Furthermore, elements from different embodiments can be combined to form other embodiments.

[0087] For example, the plasma processing device used in method MT can also be a type of plasma processing device other than capacitively coupled type. Such plasma processing devices include, for example, inductively coupled plasma processing devices, electron cyclotron resonance (ECR) plasma processing devices, or plasma processing devices that use surface waves such as microwaves to generate plasma.

[0088] The following describes the experiments conducted to evaluate the method MT. In the experiments, materials with the same properties as... Figure 3 The substrate W shown is a sample substrate with the same structure. In the experiment, the sample substrate was treated with method MT using plasma processing apparatus 1. In the experiment, the silicon-containing film SF was etched to the depth between the upper and lower surfaces of the silicon oxide film OX. The processing gas used in the experiment was a mixture of C4F8, C4F6, O2, and WF6 gases. Figure 10 This is a schematic cross-sectional view of a portion of the sample substrate after etching in the experiment. In the experiment, measurements were performed using TEM / EDX. Figure 10 The concentrations of silicon (Si) and tungsten (W), i.e., the atomic fractions of silicon (Si) and tungsten (W), are shown in regions RB and RS. Region RB includes the bottom surface of the silicon oxide film OX that defines the recess RC. Region RS includes the side surface of the silicon oxide film OX that defines the recess RC.

[0089] Figure 11 (a) is a graph showing the atomic fraction of silicon (Si) versus the atomic fraction of tungsten (W) at region RS obtained through experiments. Figure 11(b) is a graph showing the atomic fractions of silicon (Si) versus tungsten (W) at region RB, obtained experimentally. Figure 11 In (a), the horizontal axis represents the position of region RS in the horizontal direction. Figure 11 In (b), the horizontal axis represents the position of region RB in the horizontal direction. For example... Figure 11 As shown in (a), no peaks with high tungsten concentration were detected in region RS. On the other hand, as... Figure 11 As shown in (b), a high concentration peak of tungsten was detected in region RB, at the location including the bottom surface that defines the recess RC. Therefore, it is confirmed that, according to method MT, at the location including the bottom surface that defines the recess RC, a portion of the silicon atoms are replaced by tungsten atoms.

[0090] Through the foregoing description, various embodiments of the present disclosure have been described in this specification for illustrative purposes. It is understood that various modifications can be made without departing from the scope and spirit of this disclosure. Therefore, it is not intended to limit the various embodiments disclosed in this specification; the true scope and spirit are shown by the appended claims.

[0091] Explanation of reference numerals in the attached figures

[0092] 1: Plasma processing device; 10: Chamber; 16: Substrate support; 18: Base; 61: High-frequency power supply; 62: Bias power supply; GS: Gas supply unit; W: Substrate; SF: Silicon film.

Claims

1. An etching method, comprising the following steps: (a) Prepare a substrate having a silicon-containing film and place the substrate on a substrate support disposed in a cavity, wherein the silicon-containing film includes a silicon oxide film; (b) Supplying a processing gas comprising tungsten hexafluoride gas, a carbon and fluorine-containing gas, and an oxygen-containing gas into the chamber; and (c) Etching the silicon-containing film using plasma generated from the processing gas. in, The process (c) includes the following treatments: When a second negative DC voltage is not applied to the upper electrode disposed above the substrate support, a first negative DC voltage is applied to the substrate support. as well as When the first negative DC voltage is not applied to the substrate support, the second negative DC voltage is applied to the upper electrode disposed above the substrate support.

2. The etching method according to claim 1, characterized in that, The process (c) further includes the following treatments: At the bottom surface of the recess formed by the etching in the silicon-containing film, a portion of the silicon atoms in the silicon-containing film are replaced with tungsten atoms; as well as The silicon-containing film after a portion of the silicon atoms have been replaced by tungsten atoms is etched.

3. The etching method according to claim 1 or 2, characterized in that, The pressure in the chamber during step (c) is set to be less than 1.333 Pa.

4. The etching method according to claim 1 or 2, characterized in that, The flow rate of the tungsten hexafluoride gas in the processing gas is less than 5% by volume relative to the flow rate of the processing gas.

5. The etching method according to claim 1 or 2, characterized in that, The processing gas also includes nitrogen trifluoride gas.

6. The etching method according to claim 5, characterized in that, The flow rate of nitrogen trifluoride gas in the processing gas is greater than the flow rate of tungsten hexafluoride gas in the processing gas.

7. The etching method according to claim 1 or 2, characterized in that, The processing gas includes a fluorocarbon gas as the carbon and fluorine-containing gas.

8. The etching method according to claim 7, characterized in that, The silicon-containing film also includes a silicon nitride film.

9. The etching method according to claim 7, characterized in that, The silicon-containing film also includes a polycrystalline silicon film.

10. The etching method according to claim 1 or 2, characterized in that, The silicon-containing film also includes a silicon nitride film. The processing gas includes hydrofluorocarbon gas as the carbon and fluorine-containing gas.

11. The etching method according to claim 8, characterized in that, In step (c), a tungsten-containing film is formed on the sidewall of the silicon nitride film formed by the etching.

12. The etching method according to claim 1 or 2, characterized in that, The silicon-containing film includes a laminated film having the silicon oxide film and the silicon nitride film. The process (c) includes the following treatments: The silicon nitride film is etched while the bias frequency is set to a first frequency, which is the reciprocal of the time interval for applying the first negative DC voltage to the substrate support. as well as The silicon oxide film is etched while the bias frequency is set to a second frequency that is greater than the first frequency.

13. The etching method according to claim 1 or 2, characterized in that, In step (c), the temperature of the substrate support is set to a temperature above 0°C and below 120°C.

14. The etching method according to claim 1 or 2, characterized in that, In step (c), the absolute value of the first negative DC voltage applied to the substrate support is 1 kV or more and 20 kV or less.

15. The etching method according to claim 1 or 2, characterized in that, In step (c), the first negative DC voltage periodically applied to the substrate support has a duty cycle of 5% or more and 40% or less. In step (c), the reciprocal of the time interval during which the first negative DC voltage is applied to the substrate support, i.e., the bias frequency, is 100 kHz or more and 1 MHz or less.

16. The etching method according to claim 1 or 2, characterized in that, The substrate also has a base region or an etch stop layer, and the etching method further includes the following steps: (d) During the period when the substrate region or the etch stop layer is exposed, the supply of tungsten hexafluoride gas in the process gas is stopped; and (e) The silicon-containing film is etched using plasma generated from gases other than tungsten hexafluoride contained in the processing gas.

17. A plasma processing apparatus, comprising: Chamber; A substrate support is disposed within the cavity; The gas supply unit is configured to supply the chamber with a processing gas containing tungsten hexafluoride gas, a carbon and fluorine gas, and an oxygen gas. A plasma generation unit is configured to generate plasma from the processing gas within the chamber; A first bias power supply is configured to apply a first negative DC voltage to the substrate support when a second negative DC voltage is not applied to the upper electrode disposed above the substrate support; and The second bias power supply is configured to apply the second negative DC voltage to the upper electrode disposed above the substrate support when the first negative DC voltage is not applied to the substrate support.

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