JP7632967B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

This disclosure relates to a plasma processing apparatus and a plasma processing method.

Patent Document 1 proposes a plasma processing method in which a pulse wave of high frequency power for generating plasma and a pulse wave of high frequency power for biasing, which has a lower frequency than the frequency of the high frequency power for generating plasma, are applied to a mounting table. In this plasma processing method, the pulse wave of high frequency power for generating plasma and the pulse wave of high frequency power for biasing have a phase difference, and the duty ratio of the high frequency power for generating plasma is controlled to be equal to or greater than the duty ratio of the high frequency power for biasing. This provides an offset between the pulse wave of high frequency power for generating plasma and the pulse wave of high frequency power for biasing.

JP 2016-157735 A

In order to suppress or improve bowing of the etched recesses, CD size variations, mask distortion and blockage, etc., it is important to precisely control radicals, ion density, ion incidence angle, sidewall protection, etc.

This disclosure provides technology that can improve the performance of processes performed in plasma processing equipment.

According to one aspect of the present disclosure, a processing vessel capable of being evacuated to a vacuum is provided, a first electrode disposed in the processing vessel and supporting a substrate to be processed, a second electrode or an antenna disposed opposite the first electrode, a first high frequency power supply unit connected to the first electrode, the second electrode or the antenna and supplying a first high frequency power for plasma generation to the first electrode, the second electrode or the antenna, a second high frequency power supply unit connected to the first electrode and supplying a second high frequency power for bias to the first electrode, and a control unit that controls the first high frequency power supply unit and the second high frequency power supply unit, A plasma processing apparatus is provided that outputs the first high frequency power of a first level and the first high frequency power of a second level in sequence from the first high frequency power supply unit, outputs the second high frequency power of a third level from the second high frequency power supply unit during a first period before the first high frequency power of the first level is output after the first high frequency power supply unit outputs the first high frequency power of the second level, and controls the processing of a substrate to be processed by plasma generated from a processing gas supplied into the processing vessel according to the output of the first high frequency power and the second high frequency power.

According to one aspect, the performance of a process performed in a plasma processing apparatus can be improved.

1 is a schematic cross-sectional view illustrating an example of a plasma processing system according to an embodiment. FIG. 1 is a diagram showing an example of a conventional plasma processing method. 1A to 1C are views showing an example of a plasma processing method according to a first embodiment; 1A to 1C are views showing an example of a plasma processing method according to a first embodiment; FIG. 1 is a diagram for explaining the decay of radicals and the like. 10A to 10C are diagrams showing an example of a plasma processing method according to a second embodiment. 13A to 13C are diagrams showing an example of a plasma processing method according to a third embodiment. 13A to 13C are views showing an example of a plasma processing method according to a fourth embodiment. 13A to 13C are views showing an example of a plasma processing method according to a fifth embodiment. 13A to 13C are views showing an example of a plasma processing method according to a sixth embodiment.

Below, a description will be given of a mode for carrying out the present disclosure with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicate descriptions may be omitted.

[Plasma Processing System]
An example of the configuration of a plasma processing system will be described below. The plasma processing system includes a capacitively coupled plasma processing device 1 and a control unit 2. The plasma processing device 1 includes a plasma processing chamber 10 that can be evacuated, a gas supply unit 20, a power source 30, and an exhaust system 40. The plasma processing device 1 also includes a substrate support unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is disposed in the plasma processing chamber 10. The shower head 13 is disposed above the substrate support unit 11. In the embodiment, the shower head 13 constitutes at least a part of the ceiling of the plasma processing chamber 10. The inside of the plasma processing chamber 10 has a plasma processing space 10s defined by the shower head 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 has at least one gas supply port 13a for supplying at least one processing gas to the plasma processing space 10s and at least one gas exhaust port 10e for exhausting gas from the plasma processing space. The sidewall 10a is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region (substrate support surface) 111a for supporting a substrate W, such as a wafer, and an annular region (ring support surface) 111b 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 of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. In an embodiment, the main body 111 includes a base and an electrostatic chuck. 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 a substrate support surface 111a. The ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Although not shown, the substrate support 11 may 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 111a.

The shower head 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The shower head 13 also includes a conductive member. The conductive member of the shower head 13 functions as an upper electrode. In addition to the shower head 13, the gas introduction unit may include one or more side gas injectors (SGIs) attached to one or more openings formed in the side wall 10a.

The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In an embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 to the showerhead 13 via a respective flow controller 22. 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.

The power source 30 includes an RF power source 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power source 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 of the substrate support 11 and/or the conductive member of the showerhead 13. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power source 31 can function as at least a part of a plasma generating unit configured to generate plasma from one or more processing gases in the plasma processing chamber 10. In addition, by supplying a bias RF signal to the conductive member of the substrate support 11, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

In an 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 conductive member of the substrate support 11 or the conductive member of the shower head 13 via at least one impedance matching circuit, and is configured to generate a source RF signal (source RF power) for plasma generation. In an embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. In an embodiment, the first RF generating unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to the conductive member of the substrate support 11 or the conductive member of the shower head 13. The second RF generating unit 31b is coupled to the conductive member of the substrate support 11 via at least one impedance matching circuit, and is configured to generate a bias RF signal (bias RF power). In an embodiment, the bias RF signal has a lower frequency than the source RF signal. In an embodiment, the bias RF signal has a frequency in the range of 400 KHz to 13.56 MHz. In embodiments, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated bias RF signal or signals are provided to the conductive members of the substrate support 11. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

The conductive member of the base of the substrate support 11 provided in the plasma processing chamber 10 is an example of a first electrode disposed in the processing vessel and supporting the substrate to be processed. The conductive member of the shower head 13 is an example of a second electrode or antenna provided opposite the first electrode. The plasma processing system may include an inductively coupled plasma processing device instead of the capacitively coupled plasma processing device 1. In the inductively coupled plasma processing device, an antenna may be provided on the top of the plasma processing chamber 10 opposite the first electrode supporting the substrate to be processed, and the first RF generating unit 31a may be connected to the antenna.

The first RF generating unit 31a may be connected to the first electrode, the second electrode, or the antenna. The first RF generating unit 31a is an example of a first high frequency power supply unit that supplies a first high frequency power pulse (hereinafter also referred to as an "HF pulse"), which is a pulse wave of a first high frequency power for generating plasma, to the first electrode, the second electrode, or the antenna. The second RF generating unit 31b is an example of a second high frequency power supply unit that is connected to the first electrode and supplies a second high frequency power pulse (hereinafter also referred to as an "LF pulse"), which is a pulse wave of a second high frequency power for biasing, to the first electrode.

The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In an embodiment, the first DC generator 32a is connected to a conductive member of the substrate support 11 and configured to generate a first DC signal. The generated first bias DC signal is applied to the conductive member of the substrate support 11. In an embodiment, the first DC signal may be applied to another electrode, such as an electrode in an electrostatic chuck. In an embodiment, the second DC generator 32b is connected to a conductive member of the showerhead 13 and configured to generate a second DC signal. The generated second DC signal is applied to the conductive member of the showerhead 13. In various embodiments, at least one of the first and second DC signals may be pulsed. The first DC generator 32a and the second DC generator 32b are provided in addition to the RF power supply 31.

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 in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various steps described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform the various steps described herein. For example, the control unit 2 controls the first RF generating unit 31a and the second RF generating unit 31b. In an embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a memory unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on a program stored in the memory unit 2a2. The storage unit 2a2 may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a SSD (Solid State Drive), or a combination of these. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

Next, an example of a conventional plasma processing method will be described with reference to FIG. 2, and then the plasma processing methods according to the first to sixth embodiments will be described. The plasma processing methods according to the embodiments are controlled by the control unit 2. The source RF signal supplied from the first RF generating unit 31a will also be referred to as the first high frequency power, HF, or HF power. The pulse wave of the first high frequency power will also be referred to as the HF pulse. The bias RF signal supplied from the second RF generating unit 31b will also be referred to as the second high frequency power, LF, or LF power. The pulse wave of the second high frequency power will also be referred to as the LF pulse.

[Conventional Plasma Treatment Method]
2(a) and (b) are diagrams showing an example of a conventional plasma processing method. In the conventional plasma processing method, in the example of FIG. 2(a), HF is a continuous wave, and LF is a pulse wave (LF pulse). In the example of FIG. 2(b), HF and LF are pulse waves (HF pulse, LF pulse).

In the example of FIG. 2(a), the LF pulse is repeatedly turned on intermittently while the HF is turned on (supplied). In the example of FIG. 2(b), the LF pulse is turned on a predetermined period after the HF pulse is turned on, and the HF pulse is repeatedly turned on at the same timing as the LF pulse is turned off.

While HF is on, plasma and radicals are generated. While LF is on, ions in the plasma are drawn into the substrate, accelerating etching. While HF and LF are off, by-products (reaction products) generated during etching are exhausted from recesses formed in the film to be etched.

In order to achieve high anisotropic etching, i.e., verticality of the etching shape, while maintaining a high etching rate, high-output LF power is required. However, in the example of FIG. 2, while LF is on, high-output LF power is applied, and while the etching target film on the substrate is etched by high-energy ions, the mask is also scraped by the etching of the high-energy ions. In addition, a large amount of by-products adhere to the mask as the etching is promoted by the high-energy ions. This causes clogging of the mask on the etching target film. Mask clogging refers to the narrowing of the mask opening or the complete blockage of the mask opening due to by-products adhering to the sidewall of the mask. As a method for avoiding mask clogging, there is a method of turning off both HF and LF before applying HF and providing a time (Off Time) to promote exhaust.

Therefore, in the plasma processing methods according to the first to sixth embodiments described below, both HF and LF are turned off before HF is applied, providing a time (Off Time) to promote exhaust. This makes it possible to maintain the etching rate while avoiding mask clogging.

First Embodiment
[Plasma treatment method]
First, the plasma processing method according to the first embodiment will be described with reference to Fig. 3 to Fig. 5. Fig. 3 and Fig. 4 are diagrams showing an example of the plasma processing method according to the first embodiment. Fig. 5 is a diagram for explaining the attenuation of radicals and the like.

In the plasma processing methods according to the first to sixth embodiments, as shown in FIG. 3 etc., HF and LF are output as pulse waves, i.e., HF pulses and LF pulses.

As shown in FIG. 3, for example, HF has a frequency of, for example, 100 MHz and is a pulse wave (HF pulse) that repeatedly turns on and off. LF has a frequency of, for example, 13.56 MHz and is a pulse wave (LF pulse) that repeatedly turns on and off.

In the example of Figure 3, the duty ratio of the HF pulse is 20%. The duty ratio of the LF pulse is 25%. In the example of Figure 3, the HF and LF are controlled to be out of phase with each other, and the on times (supply times, application times) of the HF and LF do not overlap. Immediately after the HF is turned off (supply is stopped), there is a period during which the HF and LF are turned off (OFF time: 25% of one cycle), and then the LF is turned on.

The duty ratio of the LF pulse is 25%. After LF is turned on, there is a period during which HF and LF are turned off again (OFF time: 30% of one cycle), after which HF is turned on in the next cycle.

For the first 20% of one cycle, HF is turned on and LF is turned off (first step). For the next 25%, HF and LF are turned off (second step). For the next 25%, HF is turned off and LF is turned on (third step). For the next 30%, HF and LF are turned off (fourth step). This makes the total of each step in one cycle 100%. In the example of Figure 3, the phases of the HF pulse and the LF pulse are controlled to be shifted. The OFF time of the fourth step is necessary to promote exhaust. The OFF time of the second step is preferably set to control the ratio of radicals and ions in the plasma. After the first cycle, the same operation is repeated for the second cycle, the third cycle, and so on.

Specifically, as shown in FIG. 4, during period A when the first step is executed, HF is turned on and LF is turned off. Therefore, during period A, HF contributes to the generation of plasma and radicals, and ions, electrons, and radicals are generated, as shown in FIG. 4(a).

In addition, instead of turning off the LF during periods A, B, and D1, it may be controlled to Low. Controlling the LF to Low means controlling the LF to a power higher than 0 W and lower than the output level of the LF output during the ON time.

When LF is controlled to Low, ions can be controlled more effectively than when LF is controlled to Off. Ions cannot follow HF. On the other hand, LF has a lower frequency than HF, so ions can follow changes in LF frequency. Therefore, by controlling LF to Low, it is possible to mainly control ions.

In the following period B, in which the second step is performed, HF is turned off and LF is also turned off. In period B, the amount of radicals and ions can be controlled. FIG. 5, an enlarged view of the graph in FIG. 4(b), shows the decay of radicals, ions, and electrons. The horizontal axis of FIG. 5 is time, and the vertical axis is the normalized decay amount. When the HF power is switched from on (Power ON) to off (Power OFF), the electrons (Plasma Potential) decay rapidly first. Next, the positive ions (Plasma Density) decay. In contrast, the decay of radicals is gradual.

Thus, while electrons and ions decay relatively quickly, radicals decay relatively slowly, so that in period B, the ratio of radicals to cations increases and the ion energy decreases, allowing the amount of radicals and ions to be controlled.

Returning to FIG. 4, during period B and the following periods C and D1, HF may be controlled to Low instead of being turned off. Controlling HF to Low means outputting HF at a power higher than 0 W and lower than the output level of HF output during ON time.

When HF is controlled to Low, more radicals can be generated than when HF is controlled to Off, so radicals can be controlled. Therefore, when radical control is desired, it is better to control HF to Low than to turn it on and then off. Ions cannot follow the changes in HF, which has a higher frequency than LF. For this reason, by controlling HF to Low, it is possible to mainly control radicals.

In the following period C in which the third step is performed, HF is turned off and LF is turned on. During this period, as shown in FIG. 4(c), LF draws high-energy ions into the recesses of the film 101 to be etched. As a result, ions in the plasma are drawn into the substrate, and etching is mainly promoted by the highly energetic ions. Also, since the plasma density decreases during period B mainly due to the attenuation of electrons, ions, and radicals, when LF is turned on during period C, highly energetic ions are smoothly drawn in, promoting etching.

During period C, the ion energy is high and the etching rate is fast, so the ion incidence angle is relatively narrow and etching tends to proceed vertically, but damage to the mask 102 is likely to be significant.

In the subsequent period D1 in which the fourth step is performed, HF and LF are both turned off. During this period, by-products generated during etching in period C are exhausted from the recesses formed in the film 101 to be etched, as shown in FIG. 4(d). This allows ions and the like that have accumulated at the bottom of the recesses to be discharged, and charge cancellation occurs. In addition, as shown in FIG. 4(e), ions with low energy etch the top and sides of the mask 102, removing by-products that have adhered to the sides of the mask 102. This suppresses clogging.

According to the plasma processing method of the first embodiment, the first RF generating unit 31a outputs a first level of HF power during period A, and then repeatedly outputs a second level of HF power during periods B to D1. After the first RF generating unit 31a outputs the second level of HF power, the second DC generating unit 32b outputs a third level of LF power during a first period before the first level of HF power is output during the next period A. Through such control, the substrate W is processed by plasma generated from the processing gas supplied into the plasma processing chamber 10 according to the output of the HF and LF power. Period D1 shown in FIG. 4 is an example of the first period.

In addition, in the plasma processing method according to the first embodiment, there is a second period between the output of the second level of HF power and the output of the third level of LF power. Period B shown in FIG. 4 is an example of the second period. By providing periods in which both HF and LF are controlled to OFF or LOW in period B and period D1, it is possible to control radicals and ions and promote exhaust. Period B in each embodiment described below is an example of the second period.

In FIG. 4, period A in which HF at the first level is controlled to be on is shown as the first control of one cycle, but this is not limited to this, and period C in which LF at the third level is controlled to be on may also be the first control of one cycle. Other periods B and D1 may also be the first control of one cycle. Similarly, in each of the following embodiments, HF and LF are not limited to being controlled in order from period A. For example, after plasma ignition, depending on the process conditions, HF and LF may be controlled cyclically, starting with LF on control in period C, such as C → D1 → A → B → C...

Second Embodiment
[Plasma treatment method]
Next, a plasma processing method according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the plasma processing method according to the second embodiment.

The plasma processing method according to the second embodiment differs from the plasma processing method according to the first embodiment in that it has periods E and F in addition to periods A to D2. In other words, the control of HF and LF during periods A to D2 in the plasma processing method according to the second embodiment and the effects shown in Figures 6(a) to (e) are the same as the control of HF and LF during periods A to D1 in the plasma processing method according to the first embodiment and the effects shown in Figures 4(a) to (e).

During period A in FIG. 6, HF is turned on and LF is turned off. Therefore, during period A, as shown in FIG. 6(a), HF contributes to the generation of plasma and radicals, and ions, electrons, and radicals are generated.

In the following period B, HF is turned off and LF is turned off. In period B, as shown in Figures 5 and 6(b), electrons and ions decay relatively quickly while radicals decay relatively slowly. Therefore, in period B, the ratio of radicals to ions increases due to the difference in decay speed, and the amount of radicals and ions can be controlled.

In the following period C, HF is turned off and LF is turned on. During this time, as shown in FIG. 6(c), LF draws high-energy ions into the recesses of the film 101 to be etched. As a result, ions in the plasma are drawn into the substrate, and etching is mainly promoted by the highly energetic ions. Also, since the plasma density decreases during period B mainly due to the attenuation of electrons, ions, and radicals, when LF is turned on during period C, highly energetic ions are smoothly drawn in and etching can be promoted.

In the following F period, HF is turned on to a middle level that is lower than the output level in the A period and higher than the output level in the C period, and LF is turned on. During this period, plasma and radicals with a density lower than the plasma density shown in FIG. 6(a) are generated, and high-energy ions therein are drawn into the recesses of the etching target film 101 by LF, as shown in FIG. 6(f). As a result, ions in the plasma are drawn into the substrate, and etching is mainly promoted by the ions with high energy. In addition, by-products generated during etching are attached to the sidewalls of the recesses formed in the etching target film 101 and the sides and top of the mask 102. In addition, O ₂ gas supplied as a sidewall protective gas is dissociated by HF, and O ₂ radicals are attached to the sidewalls of the recesses and the sides and top of the mask 102. As a result, a protective film 105 is formed on the sidewalls of the recesses formed in the etching target film 101 during F period. In addition, since HF is turned off during period C, dissociation of the O ₂ gas supplied as the sidewall protective gas does not progress, and the protective film 105 is unlikely to be formed on the sidewall of the recess formed in the etching target film 101 .

In the following E period, HF is turned on to a middle level as in the F period, and LF is turned off. During this time, HF generates plasma and radicals with a lower density than that at high power due to the middle level power. As a result, as shown in FIG. 6(e), ions with low energy etch the top and sides of the mask 102, removing by-products attached to the sides of the mask. This prevents mask clogging.

In the following period D2, HF is turned off and LF is also turned off. During this period, as shown in FIG. 6(d), by-products generated during etching are exhausted from the recesses formed in the film 101 to be etched. Period D2 is an example of a third period in which the second level of HF power is output after the fourth level of HF power is output and before the first level of HF power is output.

In the plasma processing method according to the second embodiment, HF power of a first level is output in period A, HF power of a second level is output in periods B, C, and D2, and HF power of a fourth level is output in periods F and E, and this is repeated in sequence. After HF power of the second level is output, LF power of a third level is output in a third period (period D2) before HF power of the first level is output in the next period A. According to the plasma processing method according to the second embodiment, LF power of a level higher than the third level is output in period C, and then HF power of a fourth level is controlled to be output in periods F and E.

In the plasma processing method according to the second embodiment, similarly to the plasma processing method according to the first embodiment, periods in which both HF and LF are controlled to be off or low are provided before and after period A during which the first level of HF is on. This makes it possible to control radicals and ions and promote exhaust. In this embodiment, HF and LF are off during periods B and D2. Period D2 is an example of a third period before period A, and period B is an example of a second period after period A.

Furthermore, in the plasma processing method according to the second embodiment, in periods F and E, HF is controlled to a middle level that is lower than the output level in period A and higher than the output level in period B, etc. LF is turned on in period F and off in period E.

As a result, by-products generated during etching in period C adhere to the sidewalls of the recesses in the film 101 to be etched and to the sides and top of the mask 102 in period F, suppressing bowing and damage to the mask. In period E, ions with low energy etch the top and sides of the mask 102, removing the by-products adhered to the sides of the mask and suppressing clogging.

Third Embodiment
[Plasma treatment method]
Next, a plasma processing method according to a third embodiment will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of the plasma processing method according to the third embodiment.

The plasma processing method according to the third embodiment differs from the plasma processing method according to the first embodiment, which does not have period G as shown in FIG. 4, in that it has period G between period C and period D3. In other words, the control of HF and LF during periods A to D3 in the plasma processing method according to the third embodiment and the effects shown in FIGS. 7(a) to (d) are the same as the control of HF and LF during periods A to D1 in the plasma processing method according to the first embodiment and the effects shown in FIGS. 4(a) to (e).

During period A in FIG. 7, HF is turned on and LF is turned off. During this time, HF contributes to the generation of plasma and radicals, similar to the effect of period A shown in FIG. 4(a), and ions, electrons, and radicals are generated.

In the following period B, HF is turned off and LF is turned off. In period B, the ratio of radicals to ions increases due to the difference in the decay speed of electrons, ions, and radicals, similar to the effect of period B shown in Figure 4 (b), and as a result, the amount of radicals and ions can be controlled.

In the following period C, HF is turned off and LF is turned on. During this period, similar to the effect of period C shown in FIG. 4(c), LF draws high-energy ions into the recesses of the film 101 to be etched, mainly promoting etching.

In the following G period, the LF is turned on to a middle level that is smaller than the output level in the C period and larger than the output level in the D3 period, and the HF is turned off. During this period, as an effect of FIG. 7(g), although not shown, the energy of the ions drawn into the recesses of the etching target film 101 can be controlled by the difference in the power level of the LF. This changes the energy when the ions are drawn into the substrate, and the etching rate is controlled. For example, in the G period, the power of the LF is smaller than that in the C period, so the energy of the ions drawn into the recesses is also smaller, and the etching rate decreases, but the damage to the mask 102 is reduced. In addition, the amount of by-products generated during etching that adhere to the sidewalls of the recesses formed in the etching target film 101 and the sides and top of the mask 102 is controlled. The middle level LF output in the G period is an example of the fifth level LF power.

In the following period D3, LF is turned off, and HF is also turned off. During this time, as shown in FIG. 4(d), by-products generated during etching are exhausted from the recesses formed in the film 101 to be etched. Also, as shown in FIG. 4(e), ions with low energy etch the top and sides of the mask 102, removing by-products adhering to the sides of the mask 102. This suppresses clogging.

The D3 period is an example of a fourth period in which a second level of HF power is output after a fifth level of LF power is output during the G period and before a first level of HF power is output.

In the plasma processing method according to the third embodiment, HF power of a first level is output during period A, and HF power of a second level is output during periods B, C, G, and D3, and this is repeated in sequence. After HF power of the second level is output, LF power of a third level is output during a fourth period (period D3) before HF power of the first level is output during the next period A. LF power of a fifth level is output during period G immediately preceding the fourth period. In this embodiment, control is performed so that LF power of the third level is further output during the period G after LF power of the fifth level is output and before HF power of the first level is output.

According to the plasma processing method of the third embodiment, similar to the plasma processing method of the first embodiment, a period in which both HF and LF are controlled to OFF or LOW is provided in a first period before period A during which HF at a first level is ON, and in a second period after period A. This makes it possible to control radicals and ions and promote exhaust.

In addition, in the plasma processing method according to the third embodiment, in addition to the on/off control of HF and LF in the plasma processing method according to the first embodiment, the LF power is controlled to be output at a fifth level during period G, which is lower than the LF power during period C. This controls the strength of ion attraction during period G, and can control the etching rate and the amount of by-products adhering to the sidewalls of the recesses formed in the film to be etched.

Note that the middle level of LF shown in period G is an example of a fifth level of LF power. In this embodiment, the fifth level of LF power is output, and then a third level of LF power, which is lower than the fifth level, is output.

Fourth Embodiment
[Plasma treatment method]
Next, a plasma processing method according to a fourth embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of the plasma processing method according to the fourth embodiment.

The plasma processing method according to the fourth embodiment is a combination of the HF control of the plasma processing method according to the second embodiment shown in FIG. 6 and the LF control of the plasma processing method according to the third embodiment shown in FIG. 7. That is, the HF pulse controlled in the plasma processing method according to the fourth embodiment is the same as the HF pulse controlled in the plasma processing method according to the second embodiment. Also, the LF pulse controlled in the plasma processing method according to the fourth embodiment is the same as the LF pulse controlled in the plasma processing method according to the third embodiment. The control of HF and LF in the A period to D3 period of the plasma processing method according to the fourth embodiment and the effects shown in FIGS. 8(a) to (d) are the same as the control of HF and LF in the A period to D1 period of the plasma processing method according to the first embodiment and the effects shown in FIGS. 4(a) to (e). The control of HF and LF in the F period of the plasma processing method according to the fourth embodiment and the effects shown in FIG. 8(f) are the same as the control of HF and LF in the F period of the plasma processing method according to the second embodiment and the effects shown in FIG. 6(f).

In this embodiment, there is a fourth period in which LF power of a fifth level is output during the H period, and then HF power of a second level is output before HF power of a first level is output during the next A period. The D3 period is an example of the fourth period.

In the plasma processing method according to the fourth embodiment, HF power of a first level is output during period A, HF power of a second level is output during periods B, C, and D3, and HF power of a fourth level is output during periods F and H, and this is repeated in sequence. After the HF power of the second level is output, LF power of a third level is output during a fourth period (period D3) before HF power of the first level is output during the next period A. LF power of a fifth level is output during the H period immediately preceding the fourth period.

As a result, during the H period, HF is turned on to a middle level, which is the same output level as during the F period, and LF is turned on to a middle level, which is lower than the output levels during the C and F periods and higher than the output level during the D3 period.

As a result, in the plasma processing method according to the fourth embodiment, both HF and LF are controlled to a middle level during the H period. As an effect of FIG. 8(h), the middle level HF can generate plasma and radicals with a lower density than the plasma density generated by the high level HF during the A period. In addition, the middle level LF weakens the strength of attracting ions compared to the C period, allowing control of the etching rate and the amount of by-products adhering to the sidewalls of the recess formed in the film 101 to be etched and the mask 102.

Fifth Embodiment
[Plasma treatment method]
Next, a plasma processing method according to a fifth embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the plasma processing method according to the fifth embodiment.

The plasma processing method according to the fifth embodiment differs from the plasma processing method according to the fourth embodiment in that HF is controlled to be off and LF is controlled to a middle level as shown in the G period instead of the H period of the plasma processing method according to the fourth embodiment. In other words, the control of HF and LF during the A period to the D3 period and the F period of the plasma processing method according to the fifth embodiment and the effect shown in FIG. 9(a) to (d) are the same as the control of HF and LF during the A period to the D1 period of the plasma processing method according to the first embodiment and the effect shown in FIG. 4(a) to (e). The control of HF and LF during the F period of the plasma processing method according to the fifth embodiment and the effect shown in FIG. 9(f) are the same as the control of HF and LF during the F period of the plasma processing method according to the second embodiment and the effect shown in FIG. 6(f).

In the plasma processing method according to the fifth embodiment, while LF is controlled to a middle level during the G period, HF is off. LF controlled to a middle level during the G period is an example of a fifth level of LF power. The control of HF and LF during the G period and the effect shown in FIG. 9(g) are the same as the control and effect of HF and LF during the G period in the plasma processing method according to the third embodiment.

In the plasma processing method according to the fifth embodiment, HF power of a first level is output during period A, HF power of a second level is output during periods B, C, G, and D3, and HF power of a fourth level is output during period F, and this is repeated in sequence. After the HF power of the second level is output, LF power of a third level is output during a fourth period (period D3) before HF power of the first level is output during the next period A. LF power of a fifth level is output during period G immediately preceding the fourth period.

According to the plasma processing method of the fifth embodiment, during the F period, HF power of the fourth level is output, and then LF power of the fifth level is output. At this time, in the plasma processing method of the fourth embodiment, while HF power of the fourth level, i.e., middle level, is being output, LF power of the fifth level, i.e., middle level, is output. On the other hand, in the plasma processing method of the fifth embodiment, LF power of the fifth level is output after the output of HF power of the fourth level is stopped (i.e., when it is stopped).

Sixth Embodiment
[Plasma treatment method]
Next, a plasma processing method according to the sixth embodiment will be described with reference to FIG. 10. FIG. 10 is a diagram showing an example of the plasma processing method according to the sixth embodiment. In the plasma processing method according to the sixth embodiment, HF is controlled to three levels, namely, high level (800 W), middle level (500 W) and low level (250 W). It may be controlled to four levels, namely, high level, middle level, low level and off (0 W). LF is controlled to two levels, namely, on and off.

In the plasma processing method according to the second embodiment shown in FIG. 6, the fourth level, i.e., middle level, HF power is controlled to be output during the F and E periods. In contrast, in the plasma processing method according to the sixth embodiment, after middle level HF power is output during the F period, the sixth level, i.e., low level, HF power is controlled to be output during the E period.

In other words, in this embodiment, the sixth level of HF power is output after the fourth level of HF power is output and before the first level of HF power is output. Note that HF may be controlled to be off during periods B, C, and D2, or may be controlled to a power level lower than the sixth level. Note that the third level of LF power is output except during period I (period C and the first half of period F).

In the plasma processing method according to the sixth embodiment, a first level of HF power is output in period A, a second level of HF power is output in periods B, C, and D2, a fourth level of HF power is output in period F, and a sixth level of HF power is output in period E, and this is repeated in sequence. After the second level of HF power is output, a third level of LF power is output in a third period (period D2) before the first level of HF power is output in the next period A.

[Duty ratio]
The values that can be taken in the plasma processing method according to the sixth embodiment, such as the duty ratio, will be described with reference to Fig. 10. The values can also be applied to the plasma processing methods according to the first to fifth embodiments. As shown in Fig. 10 as an example, for example, the cycle period is indicated by xFeq (frequency), and xFeq is in the range of 0.1 to 2 kHz.

LF Duty, which indicates the percentage of time that LF is on during one cycle, is set in the range of 1 to 90%. Offset is 0 to 99%. The sum of LF Duty and offset is set to a value less than 100%.

HF Duty1 to Duty5 shown in FIG. 10 have a resolution of, for example, 1%. The HF power in period A is controlled to, for example, 800 W. The HF power in period A may be in the range of 50 to 2000 W. The HF power in period A may be in the range of 100 to 1000 W.

The HF power during periods B and C is controlled to, for example, 0 W, i.e., off. The HF power during periods B and C may be in the range of 50 to 2000 W. The HF power during periods B and C may be in the range of 100 to 1000 W.

The HF power during the F period is controlled to, for example, 500 W. The HF power during the F period may be in the range of 50 to 2000 W. The HF power during the F period may be in the range of 100 to 1000 W.

The HF power during the E period is controlled to, for example, 250 W. The HF power during the E period may be in the range of 50 to 2000 W. The HF power during the E period is controlled to, for example, 0 W, i.e., off. The HF power during the E period may be in the range of 100 to 1000 W.

The HF power during the D2 period is controlled to, for example, 0 W, i.e., off. The HF power during the D2 period may be in the range of 50 to 2000 W. The HF power during the D2 period may be in the range of 100 to 1000 W.

HF Duty1 in period A, HF Duty2 in period B+C, HF Duty3 in period F, HF Duty4 in period E, and HF Duty5 in period D2 can each be set in the range of 1 to 90%. HF Duty1 to Duty5 are determined so that the sum of the five duty ratios of HF Duty1 to Duty5 is 100%. The sum of the five duty ratios of HF Duty1 to Duty5 is set to a value smaller than 100%.

As described above, the plasma processing methods according to the first to sixth embodiments can be used differently depending on the type and characteristics of the process. For example, by providing a middle level of LF, the degree to which ions are attracted can be controlled by changing the power level of the LF. By using the plasma processing methods according to the first to sixth embodiments differently, the performance of the process can be improved.

The appropriate values of HF and LF, such as high level, middle level, and low level, vary depending on the type of film 101 to be etched. Therefore, the optimal HF and LF levels according to the film 101 to be etched are calculated in advance from the above-mentioned allowable power range and stored in the memory unit. The control unit 2 refers to the memory unit and controls the HF and LF levels to optimal values according to the process parameters and the type of film 101 to be etched. This can further improve the process performance.

Furthermore, by adjusting various parameters, it is possible to achieve a high selectivity ratio of the mask to the film 101 to be etched. For example, various parameters include the time of each step (on, off, etc.) of each cycle, the gas ratio of the processing gas used in the plasma processing, the set output of HF and LF (high power, low power), the pulse period of HF and LF, and the duty ratio of HF and LF.

By using the plasma processing methods according to the first to sixth embodiments and adjusting the parameters, the process performance can be improved. As an example of the process performance improvement, it is possible to improve the etching rate, suppress bowing, protect the mask, suppress mask clogging, and promote the exhaust of by-products from the recesses formed in the film 101 to be etched. As another example of the process performance improvement, it is possible to obtain high perpendicularity of holes for each process, enabling highly anisotropic etching. As a further example of the process performance improvement, it is possible to suppress the variation in the CD (Critical Dimension) value of the recesses formed in the film 101 to be etched.

The plasma processing apparatus and plasma processing method according to the embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The embodiments can be modified and improved in various ways without departing from the scope and spirit of the appended claims. The matters described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

The plasma processing apparatus disclosed herein can be applied to any type of apparatus, including Atomic Layer Deposition (ALD) apparatus, Capacitively Coupled Plasma (CCP), Inductively Coupled Plasma (ICP), Electron Cyclotron Resonance Plasma (ECR), and Helicon Wave Plasma (HWP).

REFERENCE SIGNS LIST 1 Plasma processing apparatus 2 Control unit 2a Computer 2a1 Processing unit 2a2 Memory unit 2a3 Communication interface 10 Plasma processing chamber 11 Substrate support unit 13 Shower head 21 Gas source 20 Gas supply unit 30 Power supply 31 RF power supply 31a First RF generation unit 31b Second RF generation unit 32a First DC generation unit 32b Second DC generation unit 40 Exhaust system 100 Silicon substrate 101 Film to be etched 102 Mask 111 Main body unit 112 Ring assembly

Claims (9)

a processing vessel capable of being evacuated;
a first electrode disposed in the processing chamber and supporting a substrate to be processed;
a second electrode or antenna provided opposite the first electrode;
a first high frequency power supply unit connected to the first electrode, the second electrode, or the antenna and configured to supply a first high frequency power for generating plasma to the first electrode, the second electrode, or the antenna;
a second high frequency power supply unit connected to the first electrode and configured to supply a second high frequency power for bias to the first electrode;
a control unit that controls the first high frequency power supply unit and the second high frequency power supply unit,
The control unit is
outputting the first high frequency power at a first level and the first high frequency power at a second level lower than the first level from the first high frequency power supply unit in sequence;
after the first high frequency power supply unit outputs the first high frequency power at the second level, the second high frequency power supply unit outputs the second high frequency power at a third level during a first period before the first high frequency power at the first level is output,
a second period is provided between the output of the first high frequency power at the second level and the output of the second high frequency power at the third level;
outputting the second high frequency power at the third level during the first period, and then outputting the first high frequency power at a fourth level that is lower than the first level and higher than the second level;
a third period in which the first high frequency power of the second level and the second high frequency power of a low level lower than the third level are outputted after the first high frequency power of the fourth level is outputted and before the first high frequency power of the first level is outputted,
a plasma processing apparatus that performs control so as to process a substrate to be processed with plasma generated from a processing gas supplied into the processing vessel in accordance with outputs of the first high frequency power and the second high frequency power. The control unit is
a control is performed so that the second high frequency power of a fifth level , which is lower than the third level and higher than the low level, is outputted after the second high frequency power of the third level is outputted and before the first high frequency power of the first level is outputted.
The plasma processing apparatus according to claim 1 . The control unit is
control so as to have a fourth period during which the first high frequency power at the second level is output after the second high frequency power at the fifth level is output and before the first high frequency power at the first level is output;
The plasma processing apparatus according to claim 2 . The control unit is
controlling the output of the first high frequency power at the fourth level and then the output of the second high frequency power at the fifth level;
The plasma processing apparatus according to claim 3 . The control unit is
controlling the output of the second high frequency power at the fifth level while the first high frequency power at the fourth level is being output;
The plasma processing apparatus according to claim 4 . The control unit is
control so as to stop output of the first high frequency power at the fourth level and then output the second high frequency power at the fifth level;
The plasma processing apparatus according to claim 4 . The control unit is
control so that the first high frequency power of a sixth level, which is lower than the fourth level and higher than the second level, is output after the first high frequency power of the fourth level is output and before the first high frequency power of the first level is output;
The plasma processing apparatus according to claim 1 . The LF Duty, which indicates the ratio of time that the LF is on during one cycle, is set in the range of 1 to 90%.
The plasma processing apparatus according to any one of claims 1 to 7 . a processing vessel capable of being evacuated;
a first electrode disposed in the processing chamber and supporting a substrate to be processed;
a second electrode or antenna provided opposite the first electrode;
a first high frequency power supply unit connected to the first electrode, the second electrode, or the antenna and configured to supply a first high frequency power for generating plasma to the first electrode, the second electrode, or the antenna;
a second high frequency power supply unit connected to the first electrode and configured to supply a second high frequency power for bias to the first electrode;
A plasma processing method performed in a plasma processing apparatus comprising:
outputting the first high frequency power at a first level and the first high frequency power at a second level lower than the first level from the first high frequency power supply unit in sequence;
after the first high frequency power supply unit outputs the first high frequency power at the second level, the second high frequency power supply unit outputs the second high frequency power at a third level during a first period before the first high frequency power at the first level is output,
a second period is provided between the output of the first high frequency power at the second level and the output of the second high frequency power at the third level;
outputting the second high frequency power at the third level during the first period, and then outputting the first high frequency power at a fourth level that is lower than the first level and higher than the second level;
a third period in which the first high frequency power of the second level and the second high frequency power of a low level lower than the third level are outputted after the first high frequency power of the fourth level is outputted and before the first high frequency power of the first level is outputted,
a substrate to be processed is processed with plasma generated from a processing gas supplied into the processing chamber in response to an output of the first high frequency power and the second high frequency power.
Plasma treatment method.

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