Etching method and etching apparatus

Abstract

Provided is a substrate etching method carried out using a substrate processing device. The substrate processing device comprises: a processing chamber that forms a processing space for the substrate; a substrate support body that is provided inside the processing chamber and that holds the substrate; and a power source that supplies a bias electric power to at least the substrate support body. The etching method includes: (a) a step for providing, on the substrate support body, the substrate which includes a base layer and an organic material layer on the base layer; (b) a step for generating plasma in the processing chamber; and (c) a step for supplying and stopping the supply of the bias electric power to the substrate support body repeatedly in a prescribed cycle. In step (c), the OFF time in which the bias electric power is not supplied during the cycle is set to 10 milliseconds or more.

Description

[Technical Field]

[0001] The present disclosure relates to an etching method and an etching apparatus. [Background technology]

[0002] Patent Document 1 discloses a method for controlling the critical dimension (CD) of an etching structure in an etching layer in a stack formed by a patterned photoresist mask, an intermediate mask layer disposed thereunder, a functional organic mask layer disposed thereunder, and an etching layer disposed thereunder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japan Patent Publication No. 2010-109373 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology according to the present disclosure appropriately forms high aspect ratio holes in an organic material layer that serves as a mask for forming a pattern in a layer to be etched. [Means for solving the problem]

[0005] One aspect of the present disclosure The etching apparatus includes a processing chamber, a substrate support provided in the processing chamber, a plasma generating unit, and a control unit, and the control unit executes the following steps: (a) controlling a substrate having an underlayer and an organic material layer on the underlayer on the substrate support in the processing chamber; and (b) controlling a process to form recesses in the organic material layer using plasma generated from a process gas including an oxygen-containing gas, and in the step (b), (b1) controlling a process to form recesses in the organic material layer by supplying bias power to the substrate support at a first level. The control of (b1) etching the substrate and the control of (b2) forming a protective film on the sidewall of the recess by not supplying the bias power to the substrate support or by supplying the bias power to the substrate support at a second level lower than the first level are repeatedly performed, and at least one of the frequency that defines the period of the period of the (b2) process and the proportion of the period of the (b1) process to the total period of the (b1) process and the (b2) process is controlled so that the period of the (b2) process is 10 milliseconds or more.

[0006] In the technology disclosed herein, the "duty ratio" refers to the ratio (on duty) of the ON time (time for which high frequency power is supplied) per one cycle (ON time + OFF time) of high frequency power supplied in pulses. In the technology of the present disclosure, "roundness" refers to the ratio of the minimum diameter to the maximum diameter (min diameter / max diameter) in the cross-sectional shape of a hole formed in an organic material layer. [Effects of the Invention]

[0007] According to the present disclosure, holes with a high aspect ratio can be appropriately formed in an organic material layer that serves as a mask for forming a pattern in a layer to be etched. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a vertical cross-sectional view schematically illustrating an example of the configuration of a plasma processing system. [Figure 2] 3A to 3C are explanatory views showing the state of an etching target layer and an organic material layer before and after etching processing. [Figure 3] 10A and 10B are explanatory diagrams showing the deterioration of circularity and the occurrence of bowing in an organic material layer. [Figure 4] 10 is a graph showing an example of supplying high frequency power to a substrate support. [Figure 5] FIG. 10 is an explanatory diagram showing an example of an etching process result according to an example. [Figure 6] FIG. 10 is an explanatory diagram showing an example of an etching process result according to an example. DETAILED DESCRIPTION OF THE INVENTION

[0009] In a semiconductor device manufacturing process, an etching process is performed on a layer to be etched (e.g., a silicon-containing film) formed on the surface of a semiconductor substrate (hereinafter simply referred to as "substrate") using a patterned mask layer (e.g., an amorphous carbon layer (ACL)) as a mask. The formation of a pattern on this mask layer is generally performed in a plasma processing apparatus.

[0010] The above-mentioned Patent Document 1 discloses a method for etching a mask layer (an intermediate mask layer and a functional organic layer) inside a plasma processing apparatus (an etching chamber). Specifically, an etching gas is introduced into an etching chamber into which a substrate on which a mask layer has been formed is carried, and then a high frequency wave from a radio frequency (RF) source is supplied to an electrode to generate plasma inside the etching chamber, and the intermediate mask layer and the functional organic layer are selectively etched in sequence.

[0011] When forming a pattern on a mask layer, it is important to transfer the shape of the top of the hole directly to the shape of the bottom of the hole. However, in recent years, with the trend toward finer patterns formed on substrate surfaces, it has become necessary to form holes (mask patterns) with high aspect ratios in the mask layer, which has raised concerns about the deterioration of the roundness of the bottom of the hole.

[0012] Conventionally, the method for improving roundness has been to cycle the high-frequency bias power of several hundred Hz or higher on and off. However, there is a trade-off between improving the roundness at the bottom of the hole and the occurrence of bowing on the sidewall of the hole, and this method has the problem of making it impossible to uniformly control the cross-sectional shape of the hole.

[0013] The technology disclosed herein has been made in consideration of the above circumstances, and appropriately forms high aspect ratio holes in an organic material layer that serves as a mask for forming a pattern on a layer to be etched. Hereinafter, a plasma processing system according to one embodiment and a plasma processing method including an etching method according to this embodiment will be described with reference to the drawings. Note that in this specification and the drawings, elements having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] <Plasma processing system> First, a plasma processing system according to one embodiment will be described below with reference to Fig. 1, which is a longitudinal sectional view showing an outline of the configuration of the plasma processing system.

[0015] The plasma processing system includes an inductively coupled plasma (ICP) processing apparatus 1 and a control unit 2. The plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window. The plasma processing apparatus 1 also includes a substrate support 11, a gas inlet, and an antenna 14. The substrate support 11 is disposed within the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space 10s and at least one gas exhaust port for exhausting gas from the plasma processing space 10s.

[0016] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a (substrate support surface) for supporting a substrate (wafer) W, and an annular region 111b (ring support surface) for supporting the ring assembly 112. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a, and the ring assembly 112 is disposed on the annular region 111b so as to surround the substrate W on the central region 111a.

[0017] In one embodiment, the main body 111 includes a base (not shown) and an electrostatic chuck (not shown). The base includes a conductive member. The conductive member of the base functions as a lower electrode. The electrostatic chuck is disposed on the base. The upper surface of the electrostatic chuck has the central region 111a and annular region 111b described above. The ring assembly 112 includes one or more annular members, at least one of which is an edge ring.

[0018] Although not shown, the substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck, the ring assembly 112, and the substrate W to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow path, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path. The substrate support 11 may also include a heat transfer gas supply unit configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface.

[0019] The gas inlet is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas inlet includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 13 has at least one gas supply port 13a, at least one gas flow path 13b, and at least one gas inlet port 13c. The process gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

[0020] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 through a respective flow controller 22 to the central gas inlet 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include one or more flow modulation devices to modulate or pulse the flow rate of the at least one process gas.

[0021] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to the conductive member (lower electrode) of the substrate support 11 and the antenna 14. This causes a plasma to be formed from at least one process gas supplied to the plasma processing space 10s. Thus, the RF power supply 31 can function as at least a part of a plasma generating unit configured to generate a plasma from one or more process gases in the plasma processing chamber 10. Furthermore, supplying a bias RF signal to the lower electrode generates a bias potential on the substrate W, thereby attracting ions in the formed plasma to the substrate W.

[0022] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to the antenna 14 and configured to generate a source RF signal for plasma generation (source RF power: hereinafter, sometimes referred to as "high frequency power HF") via at least one impedance matching circuit. In one embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.

[0023] The second RF generating unit 31b is coupled to the lower electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power: hereinafter, sometimes referred to as "high frequency power LF") as bias power. In one embodiment, the bias RF signal has a lower frequency than the source RF signal. In one embodiment, the bias RF signal has a frequency within a range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generating unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to the lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0024] The power supply 30 may also include, for example, a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to the lower electrode and configured to generate a bias DC signal. The generated bias DC signal is supplied to the lower electrode. In one embodiment, the bias DC signal may also be supplied to another electrode, such as an electrode in an electrostatic chuck. In various embodiments, the bias DC signal may be pulsed. Note that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0025] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to the outer coil and the inner coil separately.

[0026] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the internal pressure of the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0027] The controller 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The controller 2 may be configured to control each element of the plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, part or all of the controller 2 may be included in the plasma processing apparatus 1. The controller 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on programs stored in the storage unit 2a2. The storage unit 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0028] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0029] For example, in the present embodiment, the plasma processing system has been described as having an inductively coupled plasma (ICP) plasma processing apparatus 1, but the configuration of the plasma processing system is not limited to this. For example, the plasma processing system may have a processing apparatus including a plasma generation unit such as capacitively coupled plasma (CCP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), or surface wave plasma (SWP). Furthermore, processing apparatuses including various types of plasma generation units, including alternating current (AC) plasma generation units and direct current (DC) plasma generation units, may also be used.

[0030] <Plasma treatment method> Next, an etching process for an organic material layer performed using the plasma processing apparatus 1 configured as above will be described.

[0031] In this embodiment, as shown in FIG. 2(a), an etching target layer E (e.g., an SiOx film), a base layer G (e.g., a SiN film), an organic material layer M, and a mask pattern P are formed on a substrate W in this order from bottom to top. The organic material layer M has, for example, an amorphous carbon layer (ACL). Then, in the plasma processing apparatus 1, a pattern is formed in the organic material layer M by the etching method according to this embodiment, as shown in FIG. 2(b). Furthermore, the etching target layer E may be etched using the organic material layer M as a mask, thereby forming a pattern in the etching target layer E.

[0032] First, the substrate W is loaded into the plasma processing chamber 10 and placed on the substrate support 11. Then, a DC voltage is supplied to the electrodes in the electrostatic chuck, causing the substrate W to be electrostatically attracted to the electrostatic chuck by Coulomb force. After the substrate W is loaded, the inside of the plasma processing chamber 10 is depressurized to a desired vacuum level by the exhaust system 40.

[0033] Next, a process gas containing an etching gas for the organic material layer M is supplied from the gas supply unit 20 to the plasma processing space 10s via the central gas inlet 13. The etching gas for the organic material layer M may be at least one oxygen-containing gas selected from the group consisting of CO gas, CO2 gas, O2 gas, O3 gas, COS gas, and HO gas. The process gas may also contain a dilution gas such as Ar gas. Furthermore, the first RF generator 31a supplies high-frequency power HF for plasma generation to the antenna 14 to excite the process gas and generate plasma. Furthermore, the second RF generator 31b supplies high-frequency power LF for bias to the lower electrode to attract ions toward the substrate W, thereby etching the organic material layer M. As shown in FIG. 2(b), the organic material layer M is etched, and holes H are formed in the organic material layer M as a mask pattern. The holes H formed in the organic material layer M may also be referred to as "recesses" in the technology disclosed herein.

[0034] Here, when forming holes H with a high aspect ratio due to the recent demand for finer mask patterns, the deeper the holes H are formed, the less ions reach the bottom of the holes H. This raises concerns about the deterioration of the circularity at the bottom of the holes H, as described above. A conventional method for improving the roundness of the bottom of the hole H is to turn on and off the high-frequency bias power LF at a high frequency of several hundred Hz or more, that is, to repeat the supply and stop of the high-frequency power LF at a predetermined cycle. However, in this case, there is a risk that the sidewall of the hole H will become bowed, which is known as bowing (uneven CD value of the hole H) (see Figure 3).

[0035] In this embodiment, to prevent bowing of the hole H and to prevent deterioration of the roundness of the bottom of the hole H, high-frequency power LF, which is bias power, is supplied to the substrate support during etching in the form of pulses that are repeatedly turned on and off at a predetermined cycle. In one example, as shown in FIG. 4 , high-frequency power LF is supplied to the substrate support (lower electrode) at a frequency (hereinafter also referred to as the “pulse frequency”) of 100 Hz or less, which defines a cycle of a first period P1 during which high-frequency power LF is supplied to the substrate support (ON) and a second period P2 during which the supply of high-frequency power LF is stopped (OFF). The high-frequency power LF is supplied to the substrate support (lower electrode) at a duty ratio (P1 / (P1+P2)) of 20% to 60%. Note that the high-frequency power LF may be supplied to the substrate support (lower electrode) not as a pulse that is repeatedly turned on and off, but by high-low control as shown in FIG. 4 .

[0036] FIG. 5 is an explanatory diagram showing an example of the results of an etching process according to an embodiment, and shows the "circularity" and "bowing CD value (BB Bias: difference between the MAX CD value and the bottom CD value at hole H)" for (a) a comparative example in which high frequency power LF is supplied as a continuous wave (CW), and (b) to (e) examples in which high frequency power LF is supplied as pulses with a pulse frequency of 2 Hz to 200 Hz and a duty ratio of 50%. 6 is an explanatory diagram showing an example of the etching process results according to the embodiment, and shows the "roundness" and "bowing CD value" for (a) a comparative example in which high frequency power LF is supplied as a continuous wave, and (b) to (d) examples in which high frequency power LF is supplied as a pulse with a duty ratio of 30% to 90% and an OFF time of 50 msec (the time when high frequency power LF is not supplied in the pulse wave). Note that FIG. 6(a), which is a comparative example, is the same as the comparative example shown in FIG. 5(a).

[0037] 5(a) and 6(a), when high frequency power LF is supplied to the lower electrode in continuous wave during etching, the circularity of the bottom of hole H is improved to some extent, but bowing occurs on the sidewall. Specifically, although the bottom shape of hole H is approximately circular, a difference occurs between the MAX CD value and the bottom CD value in the cross-sectional shape, and hole H has a bowed shape.

[0038] 5(b) to (e), it can be seen that as the ON / OFF cycle of the high frequency power LF supplied to the lower electrode during the etching process becomes longer, the roundness at the bottom of the hole H improves. Specifically, at a pulse frequency of (c) 50 Hz, the roundness becomes almost the same as that of the comparative example (a), and at a pulse frequency of (d) 10 Hz or less, the roundness approaches "1." In other words, it can be seen that the difference between the maximum and minimum diameters of the hole H becomes smaller and the roundness is improved.

[0039] Next, as shown in Figures 6(b) to (d), it can be seen that the bowing of the hole H is suppressed regardless of the duty ratio of the high frequency power LF supplied to the lower electrode. Also, by comparing Figures 5(e) and 6(b), it can be seen that when the duty ratio is changed under the same pulse frequency conditions, the bowing is improved as the duty ratio decreases. In other words, it is predicted that the bowing of the hole H will tend to improve as the duty ratio of the high frequency power LF decreases. On the other hand, as shown in Figures 6(b) to (d), when the OFF time is fixed (50 msec in the example of Figure 6) and the duty ratio of the high frequency power LF is increased, the pulse frequency, which is the ON / OFF cycle of the high frequency power LF, becomes smaller, and it can be seen that the circularity tends to improve.

[0040] In this way, by supplying the high frequency power LF to the lower electrode in the form of low frequency pulses, the roundness of the bottom of the hole H can be improved and bowing occurring in the hole H can be reduced. This is thought to be because, by supplying the bias high frequency power LF in pulses, ions are actively drawn into the hole H during the ON time of the high frequency power LF, allowing etching to proceed, and the effect of drawing ions to the bottom of the hole H decreases during the OFF time, resulting in a greater effect of uniformly and firmly forming a polymer (a reaction product of the etching gas) as a protective film on the side wall of the hole H. In other words, the polymer formed during the OFF time can protect the side wall of the hole H from etching during the ON time, thereby suppressing the occurrence of bowing. Furthermore, if a low frequency is used as the high frequency power LF, the number of ions that reach the bottom of the high aspect ratio hole H can be increased, thereby promoting etching at the bottom compared to the conventional method.

[0041] As can be seen from the results shown in Figures 5 and 6, by supplying high-frequency power LF to the lower electrode in the form of a low-frequency pulse output during etching, the roundness of the hole H can be improved and bowing, which is in a trade-off relationship with this, can also be suppressed.

[0042] Returning to the description of the plasma processing of the substrate W performed using the plasma processing apparatus 1 as an example. When the mask pattern is formed by etching the organic material layer M, the supply of the high frequency power HF and the high frequency power LF from the RF power supply 31 and the supply of the processing gas from the gas supply unit 20 are stopped.

[0043] Next, a process gas containing an etching gas for the etching target layer E is supplied from the gas supply unit 20 to the plasma processing space 10s via the central gas injection unit 13. The etching gas for the etching target layer E may be at least one gas selected from the group consisting of CF4, CHF3, and O2. The process gas may also contain a dilution gas such as Ar gas. Furthermore, the first RF generator 31a supplies high-frequency power HF for plasma generation to the antenna 14, exciting the process gas to generate plasma. The generated plasma then performs an etching process on the substrate W. In this etching process, the etching target layer E and the base layer G are etched using the organic material layer M as a mask, as shown in FIG. 2(c), and a mask pattern is transferred onto the substrate W.

[0044] In the etching process of the etching target layer E, as described above, a mask pattern (hole H) is formed on the organic material layer M appropriately, i.e., with good circularity and suppressed bowing, so that the mask pattern can be appropriately transferred to the etching target layer E.

[0045] Thereafter, when the transfer of the mask pattern to the etching target layer E formed on the surface of the substrate W is completed, the etching process for the etching target layer is terminated. To terminate the etching process, first, the supply of high frequency power HF from the RF power supply 31 and the supply of processing gas by the gas supply unit 20 are stopped. Furthermore, if high frequency power LF was supplied during plasma processing, the supply of this high frequency power LF is also stopped. Next, the supply of heat transfer gas to the back surface of the substrate W is stopped, and the attraction and holding of the substrate W by the electrostatic chuck is stopped.

[0046] The substrate W that has been subjected to the etching process is then carried out of the plasma processing chamber 10 by a substrate transport mechanism (not shown), completing a series of plasma processing steps for the substrate W. Note that, although this example shows that the etching of the organic material layer M and the etching target layer E are performed in the same plasma processing apparatus 1, they may each be performed using separate plasma processing apparatuses.

[0047] As described above, according to this embodiment, by supplying bias high frequency power LF to the lower electrode as a low-frequency pulse output during etching of the organic material layer M, it is possible to appropriately improve the roundness of the bottom of the hole H (mask pattern) and suppress bowing that occurs on the sidewall of the hole H. Conventionally, when improving the roundness of these holes H, there was a trade-off relationship between the occurrence of bowing for the hole H, but according to this embodiment, by supplying high frequency power LF to the lower electrode as a low-frequency pulse output, it is possible to appropriately improve the roundness of the hole H and suppress bowing.

[0048] In addition, by controlling the pulse frequency of the high frequency power LF to be 2 Hz or more but less than 100 Hz and the duty ratio to be 20% or more but less than 90%, preferably by controlling the pulse frequency to be 2 Hz or more but less than 50 Hz and the duty ratio to be 30% or more but less than 90%, the roundness and bowing of the hole H can be further improved appropriately.

[0049] Specifically, as shown in Figures 5 and 6, it was confirmed that the hole H formed by the above etching method had a circularity of 0.90 or more and a bowing CD value (BB Bias) of 40 nm or less.

[0050] In the above embodiment, the roundness and bowing of the hole H are improved by controlling the pulse frequency and duty ratio of the high frequency power LF, but the control items in the etching process in the technology disclosed herein are not limited to this.

[0051] As shown in Fig. 5, in the above embodiment, the roundness of the hole H was improved by lowering the ON / OFF cycle (pulse frequency) while the duty ratio, which is the ratio of the ON time of the high frequency power LF, was controlled to a constant value of 50%. However, as can be seen from Fig. 5, it can be said that the roundness of the hole H can be improved by increasing the OFF time while the duty ratio, which is the ratio of the ON time of the high frequency power LF, is controlled to a constant value of 50%. In other words, the roundness of the hole H can be improved by controlling the OFF time of the high frequency power LF supplied in pulses.

[0052] Specifically, as shown in FIG. 5 , by supplying high-frequency power LF to the lower electrode in a pulsed output and controlling the OFF time of the pulsed output to 10 msec or more, the roundness and bowing of the hole H can be improved, as in the above embodiment. In one example, the pulse frequency and duty ratio of the high-frequency power LF may be set so that the OFF time of the pulsed output is 10 msec or more. For example, if a pulse frequency of 50 Hz is selected, the duty ratio may be set to 50% or less. Furthermore, if a pulse frequency of 2 Hz is selected, the duty ratio may be set to 98% or less. For example, if the duty ratio is 20%, the pulse frequency of the high-frequency power LF may be set to 80 Hz or less. If the duty ratio is 90%, the pulse frequency of the high-frequency power LF may be set to 10 Hz or less. In another example, the duty ratio of the pulsed output is preferably controlled to 20% to 60%, preferably 50%.

[0053] Summarizing the results of the above examples, it is believed that the roundness of the holes H can be improved by supplying high frequency power LF to the lower electrode in low frequency pulses and lengthening the reaction time (increasing reactivity) between the oxygen radicals generated in the plasma processing space 10s and the organic material layer M. In light of this, it is believed that the roundness of the holes H can be further improved by, for example, increasing the internal pressure or internal temperature of the plasma processing chamber 10 or increasing the oxygen-containing gas ratio in the processing gas in addition to supplying high frequency power LF in low frequency pulse output, thereby improving the reactivity between the oxygen radicals and the organic material layer M.

[0054] In the above embodiment, the second RF generator 31b supplies a bias RF signal (high frequency power LF) to the lower electrode. However, the type of bias power is not limited to this. Specifically, instead of or in addition to the bias RF signal from the second RF generator 31b, a bias DC voltage (bias DC signal) may be supplied to the lower electrode from the bias DC generator 32a of the DC power supply 32 shown in FIG. 1. The bias DC voltage may be supplied to the lower electrode so as to generate a negative potential on the substrate W. In one example, the bias DC voltage is supplied to the lower electrode as a pulse voltage having a negative polarity. In this case, the pulse voltage may be a square wave pulse, a triangular wave pulse, an impulse, or a pulse with another voltage waveform. Even when a DC voltage is supplied from the bias DC generating unit 32a to the lower electrode in this manner, by pulsing the DC voltage so that it has an OFF period of 10 milliseconds, it is possible to suppress deterioration of the roundness of the hole H and also to appropriately suppress the occurrence of bowing on the side wall of the hole H.

[0055] In the above embodiment, an example has been described in which etching processing is performed in the plasma processing apparatus 1 by ON / OFF control of the high frequency power LF. However, as described above, in the plasma processing apparatus 1, etching processing may also be performed by high-low control instead of ON / OFF control of the high frequency power LF.

[0056] Specifically, during etching, as shown in FIG. 4, a first period in which high frequency power LF, which is bias power, is supplied to the substrate support at a first level, and a second period in which high frequency power LF, which is bias power, is supplied to the substrate support at a second level lower than the first level, are repeated at a predetermined cycle. In this embodiment, the second period in which high frequency power LF is supplied at the second level (low level) corresponds to the OFF time in the above embodiment, and the effect of attracting ions to the bottom of hole H is reduced, forming a polymer as a protective film on the side wall of hole H. Furthermore, the first period during which high frequency power LF is supplied at the first level (High level) corresponds to the ON time in the above embodiment, and while the side wall of hole H is protected by the polymer (protective film) formed on the side wall of hole H, ions are actively attracted into hole H, allowing etching at the bottom to proceed.

[0057] As a result of extensive research, the inventors have confirmed that even when the supply of high frequency power LF to the substrate support is controlled between high and low levels, etching can be carried out under the same conditions as in the case of the above-mentioned ON / OFF control. That is, by controlling the duration of the second period of the cycle including the first period and the second period to 10 milliseconds or more, the circularity and bowing of the hole H can be improved as in the above embodiment. In addition, at this time, by controlling the pulse frequency of the high frequency power LF to be 2 Hz or more but less than 100 Hz and the duty ratio to be 20% or more but less than 90%, preferably by controlling the pulse frequency to be 2 Hz or more but less than 50 Hz and the duty ratio to be 30% or more but less than 90%, the circularity and bowing of the hole H can be further improved as in the above embodiment.

[0058] Specifically, it was confirmed that the hole H formed by this etching method also had a circularity of 0.90 or more and a bowing CD value (BB Bias) of 40 nm or less, similar to the etching method involving ON / OFF control shown in the above embodiment.

[0059] In addition, when high-low controlling the high-frequency power LF in this manner, the "duty ratio" refers to the ratio of the first period (the time during which the high-frequency power LF is supplied at the first level) per one cycle of the high-frequency power (first period + second time). Furthermore, the "pulse frequency" when controlling the high-frequency power LF between high and low levels refers to the frequency at which the high-frequency power is switched between high and low. In other words, the "pulse frequency" when controlling the high-low level can be said to be the pulse frequency that defines the cycle of at least one of the first period and the second period.

[0060] In the above embodiment, the organic material layer M is described as, for example, an ACL film formed on the substrate W, but the type and number of layers of the organic material layer M are not limited to this and can be set as appropriate.

[0061] Furthermore, in the above embodiment, an example has been described in which an etching target layer E and a base layer G are stacked on a substrate W, but the types and number of stacked layers of the etching target layer E and base layer G are not limited to those in the above embodiment and can be set as appropriate.

[0062] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0063] 1. Plasma processing equipment 10 Plasma Processing Chamber 10s Plasma treatment space 11 Substrate support 31 RF power supply G Base layer LF high frequency power M organic material layer W substrate

Claims

1. a processing chamber; a substrate support disposed within the processing chamber; a plasma generating unit; a control unit, The control unit (a) controlling a substrate having an underlayer and an organic material layer on the underlayer on the substrate support in the processing chamber; (b) forming recesses in the organic material layer using plasma generated from a process gas including an oxygen-containing gas; and in the step (b), (b1) controlling a bias power supply to the substrate support at a first level to etch the organic material layer; (b2) controlling the substrate support to not supply the bias power or to supply the bias power to the substrate support at a second level lower than the first level, thereby forming a protective film on a sidewall of the recess; Repeatedly execute an etching apparatus that controls at least one of a frequency that defines the period of the period of the step (b1) and a ratio of the period of the step (b1) to the total period of the step (b1) and the step (b2) so that the period of the step (b2) is 10 milliseconds or more.

2. 2. The etching apparatus according to claim 1, wherein during the step (b1), the bottom of the recess is etched while the sidewall of the recess is protected by the protective film.

3. 3. The etching apparatus according to claim 1, wherein the frequency that defines the period of the period of the step (b1) is equal to or greater than 2 Hz and less than 100 Hz.

4. 4. The etching apparatus according to claim 1, wherein the proportion of the period of the (b1) step to the total time of the period of the (b1) step and the period of the (b2) step is 20% or more and 90% or less.

5. 5. The etching apparatus according to claim 1, wherein the oxygen-containing gas includes at least one gas selected from the group consisting of CO gas, CO2 gas, O2 gas, O3 gas, COS gas, and H2O gas.

6. 6. The etching apparatus according to claim 1, wherein the processing gas further contains an inert gas.

7. 7. The etching apparatus according to claim 1, wherein the recess formed in the organic material layer in the step (b2) has a circularity of 0.90 or more and a bowing CD value of 40 nm or less.

8. 1. A method for etching a substrate, comprising: (a) providing a substrate having an underlayer and an organic material layer on a substrate support in a processing chamber; (b) forming recesses in the organic material layer using plasma generated from a process gas including an oxygen-containing gas; In the step (b), (b1) a first period of time for etching the organic material layer by supplying a bias power at a first level to the substrate support; (b2) a second time period in which the bias power is not supplied to the substrate support or the bias power is supplied to the substrate support at a second level lower than the first level to form a protective film on the sidewall of the recess; Repeat an etching method, wherein at least one of a frequency that defines a cycle of the first period and a ratio of the first period to a total of the first period and the second period is controlled so that the second period is 10 milliseconds or more.

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