Plasma processing methods using low frequency bias pulses

Abstract

A plasma processing method comprises the steps of generating plasma in a processing chamber by providing a first source power (SP) pulse to an SP coupling element for a first SP pulse duration; providing a high-frequency bias power (HBP) pulse to a substrate holder placed in the processing chamber for an HBP pulse duration that overlaps with the first SP pulse duration; and providing a first low-frequency bias power (LBP) pulse to a substrate holder for a first LBP pulse duration that does not overlap with the first SP pulse duration. The HBP pulse includes an HBP pulse frequency greater than 800 kHz. The first LBP pulse includes an LBP pulse frequency less than about 800 kHz.

Description

Technology Field

[0001] Cross-reference regarding related patents and applications

[0002] This application claims the benefit of the filing date and priority of U.S. Patent Regular Application No. 16 / 785,260 (filed February 7, 2020), the entirety of which is incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a plasma treatment method, apparatus, and system, in general, using a low-frequency bias pulse in a specific embodiment. Background Technology

[0005] Device formation within a microelectronic workpiece may involve a series of fabrication techniques including the formation, patterning, and removal of multiple material layers on a substrate. To achieve the physical and electrical specifications of current and next-generation semiconductor devices, a process flow that enables the reduction of feature size while maintaining structural integrity is desirable for various patterning processes. As device structures become vertically denser and more advanced, the demand for precision material processing is becoming stronger.

[0006] Plasma processes are commonly used to form devices, interconnects, and contacts in microelectronic workpieces. Plasma processes are used in various processing steps such as FEOL (front-end-of-line), MOL (middle-of-line), and BEOL (back-end-of-line). For example, plasma etching and plasma deposition are common process steps during semiconductor device manufacturing. A combination of source power (SP) applied to the coupling device and bias power (BP) applied to the substrate holder can be used to generate and direct the plasma. SP can be used to generate a plasma that increases the plasma temperature. Similarly, BP can be used to impart velocity to the plasma species. However, conventional plasma processes counteract these effects to separate them from each other, resulting in reduced control and precision of the process. Therefore, a plasma processing method that separates the effects of SP and BP may be desirable.

[0007] According to an embodiment of the present invention, a plasma processing method comprises the steps of generating plasma in a processing chamber by providing a first SP pulse to an SP coupling element for a first SP pulse duration; providing a high-frequency BP pulse to a substrate holder disposed in the processing chamber for a high-frequency BP pulse duration that overlaps with the first SP pulse duration; and providing a first low-frequency BP pulse to a substrate holder for a first low-frequency BP pulse duration that does not overlap with the first SP pulse duration. The high-frequency BP pulse includes a high-frequency BP pulse frequency greater than 800 kHz. The first low-frequency BP pulse includes a low-frequency BP pulse frequency less than about 800 kHz.

[0008] According to another embodiment of the present invention, a plasma processing method comprises the steps of generating plasma in a processing chamber by providing a first SP pulse to an SP coupling element for a first SP pulse duration, and providing a plurality of BP pulses to a substrate holder disposed in the processing chamber for a first BP pulse duration that does not overlap with the first SP pulse duration. Each of the plurality of BP pulses includes a BP pulse frequency of less than about 800 kHz and a BP pulse duration of less than about 10 μs.

[0009] According to another embodiment of the present invention, a plasma processing apparatus comprises a processing chamber, an SP coupling element configured to generate plasma in the processing chamber, an SP power supply node coupled to the SP coupling element and configured to supply radio frequency (RF) power to the SP coupling element, and a substrate holder disposed in the processing chamber. The plasma processing apparatus further comprises a first BP supply node coupled to the substrate holder and configured to supply first DC-biased power to the substrate holder, and a second BP supply node coupled to the substrate holder and configured to supply second DC-biased power to the substrate holder. The first DC-biased power comprises a first BP frequency of less than about 800 kHz. The second DC-biased power comprises a second BP frequency of greater than 800 kHz. Brief explanation of the drawing

[0010] To more fully understand the present invention and its advantages, refer now to the following description taken together with the accompanying drawings: FIG. 1 illustrates a schematic timing diagram of an exemplary plasma treatment method according to an embodiment of the present invention and a corresponding qualitative graph of the influence of the BP pulse frequency and BP pulse duration when combined; FIG. 2 illustrates a schematic timing diagram of another exemplary plasma treatment method according to an embodiment of the present invention, a corresponding qualitative graph of ion density and potential in a substrate, and a schematic diagram of the possible effect of a higher frequency BP pulse in a substrate; FIG. 3 illustrates a schematic timing diagram of another exemplary plasma treatment method according to an embodiment of the present invention and corresponding qualitative graphs of ion density and potential on a substrate; FIG. 4 illustrates a schematic timing diagram of various plasma treatment methods according to an embodiment of the present invention; FIG. 5 illustrates a schematic timing diagram of several plasma treatment methods and corresponding qualitative graphs of electron density and ion flux according to an embodiment of the present invention; FIG. 6 illustrates a schematic block diagram of an exemplary plasma processing system according to an embodiment of the present invention; FIG. 7 illustrates an exemplary plasma treatment method according to an embodiment of the present invention; FIG. 8 illustrates another exemplary plasma treatment method according to an embodiment of the present invention. Corresponding numbers and symbols in different drawings generally represent corresponding parts unless otherwise indicated. Drawings are illustrated to clearly exemplify related aspects of embodiments and are not necessarily drawn to scale. The edges of features illustrated in the drawings do not necessarily indicate the end of the range of the features. Specific details for implementing the invention

[0011] The fabrication and use of various embodiments are discussed in detail below. However, it should be understood that the various embodiments described herein are applicable in a wide variety of specific situations. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments and should not be interpreted as having a limited scope.

[0012] Controlling plasma characteristics can be important when implementing plasma processing methods (e.g., plasma etching and plasma deposition). Additional control can be obtained by utilizing pulsing techniques that provide source power and bias power to the processing chamber at appropriate timings. Techniques involving SP pulses and / or BP pulses may sometimes be referred to as advanced pulsing techniques (APT). APT can be implemented using one or more waveform generators and controllers to control the shape and timing of the applied power.

[0013] In particular, for example, APT may be implemented as a cyclic sequence of pulses comprising two or more loosely defined stages. An SP pulse may be applied to a coupling element (e.g., a coil of a helical resonator) to generate a high-density plasma containing ions and radicals during a first stage (e.g., an SP stage or a plasma generation stage). One or more BP pulses may be applied to a substrate holder to couple energy to ions during a second stage (e.g., a BP stage or an ion acceleration stage) and direct them toward a substrate supported by the substrate holder. A third stage (e.g., an off stage or a byproduct management stage) may be utilized in which the SP and / or BP are in an off state to allow control of byproducts within the processing chamber.

[0014] SP can be supplied as alternating current (AC) power within the radio frequency (RF) range (e.g., high frequency (HF), very high frequency (VHF), and other frequencies). BP can be supplied as direct current (DC) power (e.g., continuous DC power, pulsed DC power, bipolar DC power, etc.) or AC power (e.g., HF, medium frequency (MF), low frequency (LF), very low frequency (VLF), etc.).

[0015] Conventional plasma treatment methods are applied to both SP and BP within the HF range. However, despite the absence of SP during the BP phase, the energy imparted to ions within the plasma by the BP pulse can be minimal. Even for BP frequencies of 2 MHz (i.e., the MF range), the large volume of ions reaching the substrate surface can be nearly thermal (i.e., having negligible vertical velocity / large ion angle). For example, BP frequencies exceeding approximately 645 kHz cause the electron temperature of the plasma ( T e It can increase ) and cause parasitic plasma generation during the BP phase. Parasitic plasma generation can contribute to a lack of ion verticality because large bias voltage and large coating can cause most of the ion energy to be lost to collisions.

[0016] When a BP pulse is applied to a substrate holder, an SP coupling element (e.g., an induction coil) can function as a low-frequency return unit for the power coupled to the substrate through the substrate holder. Lower-frequency BP pulses can alter the structure of the plasma compared to higher-frequency BP pulses. A small amount of LF power within the coil can sensitively affect the plasma. For example, as BP increases, the plasma density (e.g., n e ) increases and on the other hand ( n e Both the rise time and fall time of ) can be reduced. Additionally, as SP increases relative to BP, the rise time and fall time decrease, while ( n e ) may not be substantially affected.

[0017] Due to the sensitivity of plasma characteristics to the application of BP, a wide range of conditions can generate parasitic plasma and disrupt the separation between plasma generation and ion acceleration. As BP increases, ion energy (i.e., ion temperature) also increases undesirably, which can cause an ion density distribution growing toward the substrate until parasitic plasma is generated on the substrate surface. As a specific example, in a system containing an argon (Ar) plasma with a chlorine (e.g., Cl2) additive, parasitic plasma can be generated by a BP voltage of 500 V at 800 kHz.

[0018] In various embodiments, the plasma processing method described herein includes the step of providing SP and BP to a processing chamber at different frequencies. For example, an SP pulse may be applied to an SP coupling element to generate plasma in the processing chamber, and a lower frequency BP (LBP) pulse may be applied to a substrate holder. The LBP pulse may have a frequency of, for example, less than about 800 kHz. Optionally, a higher frequency BP (HBP) pulse may also be applied. For example, the HBP pulse may have a frequency greater than 800 kHz, for example, about 13 MHz. Each of the LBP pulses may optionally be applied as a plurality of BP pulses of short duration provided after the SP pulse. For example, the duration of each of the plurality of BP pulses may be, for example, less than about 10 μs.

[0019] An exemplary plasma treatment method can advantageously separate plasma generation from the applied BP. For example, SP and BP can be advantageously separated to improve control and reduce complexity. That is, crosstalk between the source and the bias can be reduced or eliminated. The plasma treatment method described herein also advantageously substantially vertical ion velocity ( )(i.e., perpendicular to the substrate surface / small ion angle), plasma heating with little to no difference (e.g., T e ) or generation, and almost to none ion heating (i.e., small horizontal / parallel speed ( It can generate )). Therefore, ionic verticality can be beneficially maintained throughout the BP phase.

[0020] An additional advantage may be the generation of a plasma with low-temperature bulk ions that produces high density, high pressure, and a thin coating. Advantageously, the generation of little to no plasma may occur from the BP applied in the plasma treatment method described herein. BP pulses having a frequency below a specific critical frequency threshold value may advantageously extract a large ion flux from the substrate.

[0021] The embodiments provided below describe various plasma treatment methods and systems and apparatuses for performing plasma treatment methods, particularly plasma treatment methods including LBP pulses. The following description describes the embodiments. An exemplary schematic timing diagram of an exemplary plasma treatment method is described using FIG. 1. Two exemplary schematic timing diagrams of an exemplary plasma treatment method including HBP pulses are described using FIG. 2 and FIG. 3. Several additional schematic timing diagrams of an exemplary plasma treatment method are described using FIG. 4 and FIG. 5. FIG. 6 is used to describe an exemplary plasma treatment system including an exemplary plasma treatment apparatus. Two exemplary plasma treatment methods are described using FIG. 7 and FIG. 8.

[0022] FIG. 1 illustrates a schematic timing diagram of an exemplary plasma treatment method according to an embodiment of the present invention and a corresponding qualitative graph of the influence of the BP pulse frequency and BP pulse duration when combined.

[0023] Referring to FIG. 1, a schematic timing diagram (100) illustrates the application of SP and BP within a plasma processing system. At least one SP pulse (112) and at least one LBP pulse (122) are provided to the plasma processing system. In various embodiments, SP is AC power, and in some embodiments, RF power. Accordingly, each SP pulse (112) is an SP pulse frequency (indicating the frequency of the applied power). fS It has ). For example, SP pulse frequency ( f S ) may be within the HF range, VHF range, and other ranges. In one embodiment, the SP pulse frequency ( f S ) is approximately 26 MHz. In another embodiment, the SP pulse frequency ( f S ) is approximately 13 MHz.

[0024] Similarly, BP can be AC ​​power (e.g., DC biased) or DC power. Each LBP pulse (122) has an LBP pulse frequency of less than about 800 kHz ( f L It has ). LBP pulse frequency ( f L ) can be within the MF range, LF range, VLF range, and lower ranges. For example, LBP pulse frequency ( f L ) may be 0 corresponding to continuous wave (CW) DC power. Additionally, the BP delivered as DC power may be bipolar to correspond to a charging effect on the substrate. In some embodiments, the LBP pulse frequency ( f L ) is less than about 645 kHz, and in one embodiment, is about 400 kHz. LBP pulse frequency ( f L SP pulse frequency for ) f S There are no expected limits to ).

[0025] Each SP pulse (112) has an SP pulse duration ( t S ) while each LBP pulse (122) has an LBP pulse duration ( t L It has ), and the pulse duration represents the duration of each type of pulse. As illustrated, the SP pulse duration (t S ) and LBP pulse duration( t L ) do not overlap temporally. In various embodiments, the LBP pulse duration ( t L ) is less than about 100 μs and is about 80 μs in one embodiment. SP pulse duration ( t S ) and LBP pulse duration( t L There is no required relationship between ). That is, LBP pulse duration ( t L ) is the SP pulse duration ( t S It may be greater than, equal to, or less than.

[0026] A combination of appropriate timing between the SP pulse and the LBP pulse and a lower frequency of the LBP pulse can advantageously separate the effect of the applied SP from the effect of the applied BP. For example, the effect of BP in plasma generation can be reduced or eliminated in the optimal zone (11), as shown in the qualitative graph (101) of BP pulse frequency versus BP pulse duration.

[0027] The optimal zone (11) corresponds to significantly low values ​​of the BP pulse frequency and BP pulse duration. In particular, a specific threshold BP pulse frequency ( f C At values ​​exceeding ), strong coupling may exist, potentially leading to the generation of undesirable secondary plasma. For example, once 13.56 MHz BP is applied, secondary plasma may be generated on the wafer that changes the radical-to-ion ratio and, among other effects, alters the degree of sidewall passivation and / or selectivity. Critical BP pulse frequency ( f CAlthough the specific value of ) may depend on various factors, the critical BP pulse frequency ( f C ) can be approximately 645 kHz. For example, a BP pulse (e.g., impulse bias) provided as DC power at 645 kHz may not provide supplementary plasma generation and may not provide perturbation to the plasma generated by the previous SP pulse or the corresponding afterglow.

[0028] Similarly, a specific threshold BP pulse duration ( t C ) BP pulse durations exceeding ) can form strong couplings that cause undesirable plasma structural changes. For example, a possible disadvantage of longer durations is that the plasma begins to deplete, which can alter the plasma structure. Critical BP pulse duration ( t C The specific value of ) may also depend on several factors and, for example, may be from about 25 μs to about 300 μs. t C One factor that can affect a specific value of ) is that BP is the electronic temperature ( T e It is the speed of changing ). By BP ( T e The slower increase of ) is ( t C It can generate a larger value of ).

[0029] Therefore, the critical BP pulse frequency ( f C LBP pulse frequency less than ) f L ) and threshold BP pulse duration( t C LBP pulse duration less than ) t LAn LBP pulse with ) is applied to remain in the optimal zone (11) and prevent a strong coupling scenario. For example, in some cases, an LBP pulse frequency of about 400 kHz ( f L ) is, this is plasma generation or electron temperature ( T e It is a desirable frequency because it can be well separated from the increase of ). However, even if not necessary, HBP pulses can also be properly utilized in conjunction with LBP pulses and still maintain no or weak coupling as described below.

[0030] FIG. 2 illustrates a schematic timing diagram of another exemplary plasma treatment method according to an embodiment of the present invention, a corresponding qualitative graph of ion density and potential in a substrate, and a schematic diagram of possible effects of an HBP pulse in a substrate. The schematic timing diagram of FIG. 2 may be a specific embodiment of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1, for example. Similarly labeled elements may be as previously described.

[0031] Referring to FIG. 2, a schematic timing diagram (200) illustrates the application of SP and BP within a plasma processing system. SP pulse frequency ( f S ) and SP pulse duration( t S SP pulse (212) and LBP pulse frequency ( f L ) and LBP pulse duration( t LAn LBP pulse (222) having ) is provided to a plasma processing system during a pulse cycle (209) that can be repeated as needed. Specifically, the pulse cycle (209) may be performed periodically multiple times to perform a given exemplary plasma processing method. The pulse cycle (209) may have any suitable duration and is about 1 ms in one embodiment.

[0032] The pulse cycle (209) can be conceptually divided into multiple stages, such as the three stages as illustrated. An SP pulse (212) is applied to the plasma processing system during stage (201), while an LBP pulse (222) is applied during stage (202). Stage (201) may be referred to as the SP stage or the plasma generation stage. Stage (202) may be referred to as the BP stage or the ion acceleration stage. Optionally, as illustrated, a stage (203) in which the SP and BP are in an off state may also be included. Stage (203) may be referred to as the off stage or the byproduct management stage.

[0033] Additionally, an HPB pulse (232) is also provided during step (201). The HBP pulse (232) is an HPB pulse frequency ( f H ) and HPB pulse duration( t H It has ). As illustrated, the HBP pulse duration ( t H ) is the SP pulse duration ( in one embodiment t S It matches ). Alternatively, HBP pulse duration ( t H ) is the SP pulse duration ( t SIt may differ from ). Additionally or alternatively, the HBP pulse (232) may also be applied during other steps as described below. For example, the HBP pulse (232) may also be applied during step (202). HPB pulse frequency ( f H ) is the LBP pulse frequency ( f L ) exceeds. For example, in various embodiments, ( f L ) is less than approximately 800 kHz, and on the other hand ( f H ) is greater than 800 kHz. In some embodiments, ( f H ) is within the HF range and is about 13.56 MHz in one embodiment.

[0034] The pulse is the ion density on the substrate ( n i ) and root mean square potential( V rms It can have the effect of ). For example, as shown in the qualitative graph (205), ion density ( n i ) is increased during the SP pulse (212) in step (201). Because the LBP pulse (222) is separated from the generated plasma, the ion density ( n i ) is reduced during the step (202) that corresponds to afterglow. In contrast, the potential at the substrate ( V rms ) is relatively low and constant in step (201), but increases in step (202) by the application of the LBP pulse (222). After the afterglow, the ion density ( n i ) gradually decreases, while the potential ( V rms ) is rapidly reduced to nearly 0 during the stage (203) when there is no power applied.

[0035] The pulse timing shown in the schematic timing diagram (200) can advantageously be used in a plurality of plasma processing methods (e.g., for logic manufacturing), such as thin etching, profile etching (e.g., management of thin top and bottom corner rounding) and patterning (e.g. silicon nitride, silicon oxide, silicon), as well as in a plurality of patterning applications.

[0036] HBP pulses may be desirable for changing and / or changing the radical generation rate (e.g., Cl) or for influencing the etching profile. HPB pulses may also advantageously be used to manage the hygiene of a given plasma process (e.g., during SP application during the expected process). For example, passivation of a horizontal surface may be controlled using HPB pulses. Now, referring to schematic diagram (206), a mask (55) may outline an etching zone of a substrate (256) containing features such as trenches and holes with sidewalls. It may be desirable to reduce or prevent etching of the sidewalls by forming a passivation layer (57). In some embodiments, the passivation layer (57) is an oxide. While an oxide may be beneficial for sidewall protection, it may reduce the etching rate and pose a risk of etching interruption when formed on a horizontal surface. As illustrated in the schematic diagram (206), the HBP pulse (232) during step (201) can reduce or prevent the formation of a passivation layer (57) on the horizontal surface of the substrate (256), which can advantageously help manage the etching front portion.

[0037] The HBP pulse (232) is off in step (202), while the LBP pulse (222) is on. Different BP frequencies can be beneficial at different stages of a given plasma process. For example, in some cases, providing a purely lower frequency BP during the bias step may be advantageous to facilitate increased separation. However, the HBP pulse (232) can also be extended to and through both step (202) and step (203). Similarly, providing a higher frequency BP during the source step can advantageously control surface interactions on the substrate surface (e.g., by suppressing oxide formation on horizontal surfaces such as the bottom of the feature). For example, applying HBP together with SP can change the potential (plasma potential ( V PP ) and DC potential( V DC )) can be maintained, and on the other hand, LBP (e.g., 400 kHz) in the afterlight ( V PP Maximizes ). As discussed above, the HBP pulse can also be omitted (e.g., when control of the potential at the substrate during the source phase is less important).

[0038] One specific embodiment of the plasma treatment method illustrated using the schematic timing diagram (200) may be silicon (Si) etching using a 50:50 HBr and Ar gas mixture with CF4 and O2 additives. In this specific example, the SP pulse (212) is an SP pulse power of about 500 W ( P S It can be authorized by ), and ( t S ) is about 20 μs and ( f S ) is within the HF range (e.g., 13.56 MHz, 26 MHz, etc.). The HBP pulse (232) is the SP pulse (212)( t H= 20 μs) and simultaneously, for the same duration, an HBP pulse power of approximately 100 W ( P H It can be authorized by ) and ( f H ) is approximately 13.56 MHz. The LBP pulse (222) has a longer duration ( t L LBP pulse power of approximately 500 W for 80 μs ( P L It can be authorized by ) and ( f L ) is about 400 kHz. Step (203) can be implemented as an off step to control byproducts and can have a duration of about 900 μs. Thus, in this particular example, the duration of the pulse cycle (209) can be about 1 ms.

[0039] FIG. 3 illustrates a schematic timing diagram of another exemplary plasma treatment method according to an embodiment of the present invention and corresponding qualitative graphs of ion density and potential on a substrate. The schematic timing diagram of FIG. 3 may be a specific embodiment of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1, for example. A similarly labeled element may be as previously described.

[0040] Referring to FIG. 3, a schematic timing diagram (300) illustrates the application of SP and BP within a plasma processing system. The SP pulse (312), HBP pulse (332), and LBP pulse (322) are provided to the plasma processing system during a pulse cycle (309) that can be repeated as needed. Unlike the schematic timing diagram (200) of FIG. 2, the HBP pulse duration ( t H) is equal to the duration of the pulse cycle (309) in the schematic timing diagram (300). The application of this HBP may be low power and may be related to maintaining plasma ignition. For example, in cases where ignition problems (e.g., low pressure, long off phase, etc.) may exist, a low-power HBP may be desirable to maintain a small amount of plasma to facilitate reliable re-ignition of the plasma during the subsequent source phase.

[0041] The qualitative graph (305) shows the ion density ( n i ) and potential( V rms It indicates the effect of the extended duration of the HBP pulse (332) on ). As illustrated, ( n i )and ( V rms ) behaves similarly in steps (301) and (302) as in the corresponding steps (201) and (202) of FIG. 2. However, in step (303), ( n i )and ( V rms Both are maintained at a relatively constant non-zero value by the HBP pulse (332). n i )and ( V rms Compared to step (203) of Fig. 2, where both can be ignored, the ion density ( n i ) can be maintained at a desirable level by an HBP pulse (332) in step (303) corresponding to the low-density plasma. This “tickle” plasma can advantageously enable easier ignition immediately after step (303).

[0042] Additionally, it should be noted that in this case, the HBP pulse (332) is maintained through step (302), which can increase the ion flux at this stage. However, the HBP may also be turned off during step (302) in some cases. The feasibility of maintaining the HBP pulse during step (302) may depend on the effect of byproduct redeposition for a given process.

[0043] FIG. 4 illustrates a schematic timing diagram of various plasma processing methods according to an embodiment of the present invention. The schematic timing diagram of FIG. 4 may be a specific embodiment of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1. Similarly labeled elements may be as previously described.

[0044] Referring to FIG. 4, some schematic timing diagrams represent incomplete sampling of scenarios regarding the timing and power of SP, HBP, and LBP for various plasma processing methods. Each of Figures (a) through (i) includes at least one SP pulse (412) and LBP pulse (422) and is conceptually divided into three stages (stage 1, stage 2, and stage 3). The figures differ from one another in that they may include various HBP pulses and additional SP pulses with various durations and timings.

[0045] Figure (a) illustrates a scenario similar to the scenario of Figure 3, except that the HBP pulse (433) is applied for a duration that is extended through steps 1 and 2 and partially through step 3. Figures (b) and (c) illustrate two alternative scenarios in which the HBP pulse (434) is applied for a duration that is extended only partially through step 2 and the HBP pulse (435) is applied for a duration that ends simultaneously with the LBP pulse (422). In these and other scenarios, the HBP pulse may be used primarily to maintain ignition rather than to impart energy (i.e., acceleration) to the ions.

[0046] In the same way, Figure (d) illustrates a scenario similar to that of Figure 2, in which an HBP pulse (432) is applied simultaneously with the SP pulse (412), but an additional HBP pulse (436) is also applied simultaneously with the LBP pulse (422). Thus, the timing scenario illustrated in Figure (d) is similar to Figure (c), except for the interval during which the HBP is off between the SP pulse (412) and the LBP pulse (422). In Figure (d), the HBP pulse (432) and the additional HBP pulse (436) are shown to have the same power. However, this is not necessarily the case. For example, a lower power HBP pulse (437) may be supplied during the LBP pulse (422), as illustrated in Figure (e).

[0047] Drawing (f) illustrates a scenario similar to the scenario of Drawing (a) for a low-power SP pulse (416). For example, the SP pulse (412) has a first SP pulse power of about 500 W ( P S1 ) can have, on the other hand, a low-power SP pulse (416) has a second SP pulse power of about 100 W ( P S2 Can have ). P S1 )class ( P S2Any relationship between ) can be used and may depend on the specific requirements of a given plasma treatment method. For example, ( P S1 ( about ) P S2 Lower power of ) can be used to provide a small amount of additional plasma. In addition, continuous low-power SP pulses (417) can also be applied through both step 2 and step 3 as shown in figures (g), (h) and (i). When the SP is on in step 3, this can lower the ion density and increase the ion flux, which may also be desirable in some cases.

[0048] In reality, it should be noted that while there may be a delay between the SP pulse (412) and the low-power SP pulse (416), there may also be no delay as illustrated. For example, the delay may be about 5 μs or any other value. Factors such as the frequency and duty cycle of the applied SP may affect the value of the delay between the SP pulse (412) and the subsequent SP pulse (i.e., the low-power SP pulse (416), the successive low-power SP pulse (417)).

[0049] Although a wide variety of timing scenarios are illustrated in FIG. 4, any suitable combination of this embodiment and any other embodiment described herein may be made to include at least one SP pulse and at least one LBP pulse to meet the specific requirements of a specific application of the invention. As illustrated, the HBP pulse does not need to start simultaneously with the SP pulse or the LBP pulse. That is, the start of any of the illustrated HBP pulses may be offset from the time of the SP pulse or the LBP pulse in a similar manner to offset the timing of the end of the HBP pulse illustrated in FIG. 4.

[0050] FIG. 5 illustrates a schematic timing diagram of several plasma treatment methods and corresponding qualitative graphs of electron density and ion flux according to an embodiment of the present invention. The schematic timing diagram of FIG. 5 may be a specific embodiment of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1, for example. A similarly labeled element may be as previously described.

[0051] Referring to FIG. 5, the schematic timing diagram (501) illustrates the application of the SP pulse (512) without applying the BP. Electron density ( n e The corresponding qualitative graph of ) and ion flux is ( n e ) indicates that the ion flux is high during the SP pulse (512) and then decreases after the SP ends. The ion flux decreases rapidly, while ( n e ) decreases at a gradually and substantially constant rate. LBP pulse duration after SP pulse (512) ( t L The introduction of the LBP pulse (522) into ) is as shown in the schematic timing diagram (502) ( n e ) can change the rate at which it decreases. In particular, sufficiently long ( t L The LBP pulse (522) perturbs the plasma, causing it to be depleted more quickly. For example, the ion flux can mirror the background plasma density. However, it may be desirable to generate more ion flux (e.g., a dose) before applying another SP pulse.

[0052] For example, a sufficiently short LBP pulse can affect the ion flux without strongly perturbing the background plasma. That is, the impulse bias extracts the flux but does not perturb the afterglow. This is because a sufficiently short LBP pulse (i.e., LBP spike (526)) ( n e It can be seen from the schematic timing diagram (503) which indicates the generation of a corresponding sharp peak in the ion flux without affecting the ) As illustrated, the LBP spike (526) increases the ion flux while increasing the background plasma (i.e., n e A sufficiently short LBP spike duration to provide minimal or no effect on ) t k It has ). In various embodiments, ( t K ) is less than 20 μs and less than 10 μs in some embodiments. In one embodiment, ( t K ) is approximately 10 μs. In another embodiment, ( t K ) is approximately 1 μs.

[0053] The LBP spike (526) may be similar to the LBP pulse as previously described, but with a shorter duration (i.e., t K ...has ). For example, the LBP spike (526) may be a BP applied at a frequency of less than about 645 kHz (e.g., 400 kHz). Additionally, and also similar to the previously described LBP pulse, the LBP spike (526) may also be CW DC power. For example, in one embodiment, the LBP spike (526) has an LBP spike duration of about 10 μs ( t KIt is the application of CW DC power. In other embodiments, CW DC power may be applied for a longer or shorter duration.

[0054] A long LBP pulse can cause parasitic plasma generation and / or alters the plasma structure as previously described. However, parasitic plasma generation can be increased more gradually with respect to the BP "pulse train". Thus, as illustrated in the schematic timing diagram (504), a number of appropriately spaced LBP spikes (526) can advantageously generate a relatively constant ion flux without depleting the afterglow. For example, a train of doses in energy (e.g., gradually increasing as background density decreases) can advantageously generate more single-energy beams.

[0055] The spacing between adjacent LBP spikes (526) t D ) is particularly due to various factors, e.g., the frequency of the applied BP and ( t K It can be dependent on the length of ). However, ( t D ) is designed to prevent background plasma perturbation (e.g., electron temperature ( T e It can be selected to be sufficiently short so as not to raise ). For example, ( t D ) in various embodiments ( t K It is longer than ). In some embodiments, ( t D ) is about 20 μs to about 100 μs. In another embodiment, ( t D ) is about 10 μs to about 50 μs.

[0056] In some cases, surface charging can be a problem when applying LBP pulses and / or LBP spikes (e.g., to a dielectric substrate, etc.). The magnitude of the charging effect may depend on the material contained in the given substrate, and in some cases, the charge may be sufficiently dissipated between LBP spikes. However, in other cases, it may be desirable to counteract the undesirable charging effect by using bipolar DC power for the LBP spikes (526). For example, all different LBP spikes may be positive, or different patterns may be used, such as - - - - + + +, - - +, etc. Additionally, the duration of the positive LBP spikes may differ from the duration of the negative LBP spikes. Furthermore, although three LBP spikes (526) are shown, there is no intended limit on the number of LBP spikes (526). The number of LBP spikes (526) per cycle may depend on the pulse cycle time, dosage requirements, and other considerations specific to the given application.

[0057] In addition to multiple LBP spikes (526), ​​HBP pulses (532) may also be included to facilitate chemical reaction control, while SP is in the ON state as illustrated in the schematic timing diagram (505). As illustrated, during the SP pulse (512), the ion flux may be minimally affected by the potential introduced by the HBP pulse (532). This scenario can combine the benefits of the previously described HBP power with the benefits of LBP spikes. It should be noted that LBP spikes may be included in any timing configuration among the timing configurations described. That is, the scope of the invention is intended to include LBP spikes as any embodiment of any LBP described herein.

[0058] FIG. 6 illustrates a schematic block diagram of an exemplary plasma processing system according to an embodiment of the present invention. The plasma processing system and plasma processing apparatus of FIG. 6 may be used to implement any of the schematic timing diagrams for performing the exemplary plasma processing methods described herein, such as the schematic timing diagrams of FIG. 1 through 5, for example. Furthermore, the plasma processing system and plasma processing apparatus of FIG. 6 may be used to perform any of the exemplary methods described herein, such as the plasma processing methods of FIG. 7 and FIG. 8, for example.

[0059] Referring to FIG. 6, the plasma processing system (600) includes a plasma processing device (50) comprising an SP coupling element (60) (e.g., an induction coil, a helical resonator, etc.) coupled to a processing chamber (54). Although shown as an induction coil located outside the quartz window (52) of the plasma processing device (50), the SP coupling element (60) may also be implemented as a conductive plate inside the processing chamber (54) as well as any other suitable configuration (e.g., an antenna, an electrode, a waveguide, an electron beam, etc.). The SP coupling element (60) is configured to couple the SP to the processing chamber (54) so ​​that a plasma (58) is generated inside the processing chamber (54). The plasma (58) may be any type of plasma, such as inductively coupled plasma (ICP), capacitively coupled plasma (CCP), surface wave plasma (SWP), and other plasmas.

[0060] A substrate holder (70) (e.g., an electrostatic chuck) is placed within a processing chamber (54). The substrate holder (70) is configured to support a substrate (65). The substrate holder (70) is also configured to combine a BP with the processing chamber (54). The combined BP may include both HBP and LBP as described herein.

[0061] SP can be supplied to a processing chamber (54) using an SP control path comprising an SP supply node (62) coupled to an SP controller (64) and an SP coupling element (60). The SP supply node (62) may also be coupled to a waveform generator or may include a waveform generator. Additionally, the SP supply node (62) and the SP controller (64) may also be coupled. Any SP matching stage (65) may also be included between the SP coupling element (60) and the SP supply node (62).

[0062] Similarly, HBP and LBP may be supplied to the processing chamber (54) using a separate or combined BP control path comprising an HBP controller (74) and an LBP controller (84) as illustrated, as well as an HBP supply node (72) and an LBP supply node (82) coupled to the substrate holder (70). As with SP, one or both of the HBP supply node (72) and the LBP supply node (82) may also be coupled to or include their respective waveform generators. Also, as previously described, any HBP matching stage (75) and / or any LBP matching stage (85) may be included between the substrate holder (70) and the corresponding supply node. In some cases (e.g., for bipolar DC LBP pulses / spikes), the LBP supply node (82) may be divided into a positive LBP power supply and a negative LBP power supply.

[0063] The controllers (i.e., SP controller (64), HBP controller (74), LBP controller (84)) are configured to control the timing of the pulses during the cyclic plasma process. The relative timing is fully customizable as previously described. Each of the SP pulse, HBP pulse, and LBP pulse may be in phase, partially overlap, or out of phase with respect to each other.

[0064] FIG. 7 illustrates an exemplary plasma treatment method according to an embodiment of the present invention. The plasma treatment method of FIG. 7 may be performed using an exemplary schematic timing diagram and an exemplary plasma treatment system and apparatus as described herein. For example, the plasma treatment method of FIG. 7 may be combined with any embodiment of FIG. 1 through 6. The method steps below may be performed in any suitable order as may be apparent to those skilled in the art.

[0065] Referring to FIG. 7, step (701) of the plasma processing method (700) comprises generating plasma in a processing chamber by providing an SP pulse to an SP coupling element for an SP pulse duration. Step (702) comprises providing an HBP pulse to a substrate holder placed in the processing chamber for an HBP pulse duration that overlaps with the SP pulse duration. The HBP pulse has an HBP pulse frequency greater than 800 kHz. Step (703) comprises providing an LBP pulse to the substrate holder for an LBP pulse duration that does not overlap with the SP pulse duration. The LBP pulse has an LBP pulse frequency less than about 800 kHz.

[0066] FIG. 8 illustrates another exemplary plasma treatment method according to an embodiment of the present invention. The plasma treatment method of FIG. 8 may be performed using an exemplary schematic timing diagram and an exemplary plasma treatment system and apparatus as described herein. For example, the plasma treatment method of FIG. 8 may be combined with any of the embodiments of FIG. 1 through 6. Furthermore, the plasma treatment method of FIG. 8 is not intended to be mutually exclusive with other plasma treatment methods described herein. For example, the plasma treatment method of FIG. 8 may be combined with the plasma treatment method of FIG. 8. The method steps below may be performed in any suitable order as may be obvious to those skilled in the art.

[0067] Referring to FIG. 8, step (801) of the plasma processing method (800) comprises generating plasma in a processing chamber by providing an SP pulse to an SP coupling element for an SP pulse duration. Step (802) comprises providing a plurality of BP pulses to a substrate holder placed in the processing chamber for a BP pulse duration that does not overlap with the SP pulse duration. Each of the plurality of BP pulses has a BP pulse frequency of less than about 800 kHz and a BP pulse duration of less than about 10 μs.

[0068] Exemplary embodiments of the present invention are summarized herein. Other embodiments may also be understood from the specification as well as from all of the claims submitted herein.

[0069] Example 1. A plasma processing method comprising: providing a first source power (SP) pulse to an SP coupling element for a first SP pulse duration to generate plasma in a processing chamber; providing a high-frequency bias power (HBP) pulse to a substrate holder disposed in the processing chamber for an HBP pulse duration that overlaps with the first SP pulse duration, wherein the HBP pulse comprises an HBP pulse frequency greater than 800 kHz; and providing a first low-frequency bias power (LBP) pulse to a substrate holder for a first LBP pulse duration that does not overlap with the first SP pulse duration, wherein the first LBP pulse comprises an LBP pulse frequency less than about 800 kHz.

[0070] Example 2. A plasma treatment method in Example 1, wherein the HBP pulse duration completely overlaps with both the first SP pulse duration and the first LBP pulse duration.

[0071] Example 3. A plasma treatment method in which, in Example 1, the HBP pulse duration completely overlaps and is identical to the first SP pulse duration.

[0072] Example 4. A plasma processing method in any one of Examples 1 to 3, further comprising the step of providing a second SP pulse to an SP coupling element for a second SP pulse duration that overlaps with a first LBP pulse duration after a first SP pulse duration; wherein the first SP pulse includes a first SP pulse power; and the second SP pulse includes a second SP pulse power less than the first SP pulse power.

[0073] Example 5. A plasma treatment method in any one of Examples 1 to 4, wherein the first SP pulse duration is about 20 μs and the first LBP pulse duration is about 80 μs.

[0074] Example 6. A plasma processing method comprising, in any one of Examples 1 to 5, a step of providing a second SP pulse to an SP coupling element for a second SP pulse duration after a first LBP pulse duration; and a step of providing a second LBP pulse to a substrate holder for a second LBP pulse duration that does not overlap with the second SP pulse duration.

[0075] Example 7. A plasma treatment method according to Example 6, further comprising the step of not providing SP to the SP coupling electrode and not providing LBP to the substrate holder for a delay duration after the first LBP pulse duration; wherein the second SP pulse is provided after the delay duration.

[0076] Example 8. In Example 7, the HBP pulse duration completely overlaps with the first SP pulse duration and the first LBP pulse duration, and at least partially overlaps with the delay period; and the HBP pulse comprises an HBP power less than the LBP pulse power of the first LBP pulse, a plasma treatment method.

[0077] Example 9. A plasma processing method comprising: a step of generating plasma in a processing chamber by providing a first source power (SP) pulse to an SP coupling element for a first SP pulse duration; and a step of providing a plurality of bias power (BP) pulses to a substrate holder disposed in the processing chamber for a first BP pulse duration that does not overlap with the first SP pulse duration, wherein each of the plurality of BP pulses comprises a BP pulse frequency of less than about 800 kHz and a BP pulse duration of less than about 10 μs.

[0078] Example 10. A plasma processing method according to Example 9, further comprising the step of providing a high-frequency bias power (HBP) pulse to a substrate holder during a second BP pulse duration that overlaps with the SP pulse duration, wherein the HBP pulse comprises a frequency greater than 800 kHz.

[0079] Example 11. A plasma treatment method in which, in Example 10, the second BP pulse duration completely overlaps and is identical to the SP pulse duration.

[0080] Example 12. A plasma processing method comprising, in any one of Examples 9 to 11, providing a second SP pulse to an SP coupling element for a second SP pulse duration after a first BP pulse duration; and providing a second plurality of BP pulses to a substrate holder for a second BP pulse duration that does not overlap with the second SP pulse duration.

[0081] Example 13. A plasma treatment method in which, in any one of Examples 9 to 12, each of the plurality of BP pulses is a single direct current (DC) pulse.

[0082] Example 14. A plasma treatment method according to Example 13, wherein some of the plurality of BP pulses are positive DC pulses and the remainder of the plurality of BP pulses are negative DC pulses.

[0083] Example 15. A plasma treatment method in any one of Examples 9 to 14, wherein each of the plurality of BP pulses includes a BP pulse duration of less than about 1 μs.

[0084] Example 16. A plasma processing apparatus comprising: a processing chamber; a source power (SP) coupling element configured to generate plasma in the processing chamber; an SP power supply node coupled to the SP coupling element and configured to supply radio frequency (RF) power to the SP coupling element; a substrate holder disposed in the processing chamber; a first bias power (BP) supply node coupled to the substrate holder and configured to supply a first DC biased power to the substrate holder, wherein the first DC biased power comprises a first BP frequency of less than about 800 kHz; and a second BP supply node coupled to the substrate holder and configured to supply a second DC biased power to the substrate holder, wherein the second DC biased power comprises a second BP frequency of greater than about 800 kHz.

[0085] Example 17. A plasma processing apparatus in which, in Example 16, the first BP frequency is approximately 400 kHz.

[0086] Example 18. A plasma processing apparatus in which, in either Example 16 or Example 17, the second BP frequency is approximately 13 MHz.

[0087] Example 19. In any one of Examples 16 to 18, the SP coupling element is a helical resonator disposed outside the processing chamber and configured to generate inductively coupled plasma in the processing chamber; and the RF power includes an RF power frequency equal to about 27 MHz, a plasma processing apparatus.

[0088] Example 20. A plasma processing apparatus in any one of Examples 16 to 19, wherein the first BP supply node and the second BP supply node are configured to simultaneously supply the first DC-biased power and the second DC-biased power to a substrate holder.

[0089] Although the present invention has been described with reference to exemplary embodiments, this description is not intended to be interpreted in a limiting sense. By referring to the description, various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will be apparent to those skilled in the art. Accordingly, the appended claims are intended to include any such modifications or embodiments.

Claims

Claim 1 A plasma processing apparatus comprising: a processing chamber; a source power (SP) coupling element configured to generate plasma in the processing chamber; an SP supply node coupled to the SP coupling element and configured to supply radio frequency (RF) power to the SP coupling element; a substrate holder disposed in the processing chamber; a first bias power (BP) supply node coupled to the substrate holder and configured to supply a first DC-biased alternating current (AC) power to the substrate holder, wherein the first DC-biased AC power includes a first BP frequency of less than about 800 kHz; and a second BP supply node coupled to the substrate holder and configured to supply a second DC-biased AC power to the substrate holder, wherein the second DC-biased AC power includes a second BP frequency of greater than 800 kHz. Claim 2 A plasma processing apparatus according to claim 1, wherein the first BP frequency is approximately 400 kHz. Claim 3 A plasma processing apparatus according to paragraph 2, wherein the second BP frequency is approximately 13 MHz. Claim 4 A plasma processing apparatus according to claim 3, wherein the SP coupling element is a helical resonator disposed outside the processing chamber and configured to generate inductively coupled plasma in the processing chamber, and the RF power includes an RF power frequency equal to about 27 MHz. Claim 5 A plasma processing apparatus according to claim 1, wherein the first BP supply node and the second BP supply node are configured to simultaneously supply the first DC-biased AC power and the second DC-biased AC power to the substrate holder. Claim 6 A plasma processing apparatus according to claim 1, wherein the first BP frequency exceeds 0 Hz. Claim 7 A plasma processing apparatus according to claim 1, wherein the SP supply node is additionally configured to supply the RF power as an SP pulse during the SP pulse duration, the first BP supply node is additionally configured to supply the first DC-biased AC power as an LBP pulse during a low-frequency bias power (LBP) pulse duration that does not overlap with the SP pulse duration, and the second BP supply node is additionally configured to supply the second DC-biased AC power as an HBP pulse during a high-frequency bias power (HBP) pulse duration that overlaps with at least a portion of the SP pulse duration. Claim 8 A plasma processing apparatus comprising: a processing chamber; a source power (SP) coupling element configured to generate plasma in the processing chamber; an SP supply node coupled to the SP coupling element and configured to generate the plasma by supplying an SP pulse to the SP coupling element for an SP pulse duration; a substrate holder disposed in the processing chamber; and an LBP supply node coupled to the substrate holder and configured to supply a plurality of AC bias power (BP) pulses to the substrate holder for a low frequency bias power (LBP) pulse duration that does not overlap with the SP pulse duration, wherein each of the plurality of AC BP pulses includes a BP pulse frequency of less than about 800 kHz and a BP pulse duration of less than about 10 μs. Claim 9 A plasma processing apparatus according to claim 8, further comprising an HBP supply node coupled to the substrate holder and configured to supply an HBP pulse to the substrate holder during a high frequency bias power (HBP) pulse duration that overlaps with the SP pulse duration, wherein the HBP pulse comprises an HBP frequency greater than 800 kHz. Claim 10 A plasma processing apparatus according to claim 9, wherein the LBP supply node and the HBP supply node are configured to simultaneously supply DC-biased AC power to the substrate holder. Claim 11 A plasma processing apparatus according to claim 9, wherein the HBP frequency is approximately 13 MHz. Claim 12 A plasma processing apparatus according to claim 8, wherein some of the plurality of AC BP pulses are positive DC-biased pulses and the remainder of the plurality of AC BP pulses are negative DC-biased pulses. Claim 13 A plasma processing apparatus according to claim 8, wherein each of the plurality of AC BPs includes a BP pulse duration of less than about 1 μs. Claim 14 A plasma processing apparatus according to claim 8, wherein the SP coupling element is a helical resonator disposed outside the processing chamber and configured to generate inductively coupled plasma in the processing chamber, and the SP pulse comprises RF power having an RF power frequency equal to about 27 MHz. Claim 15 A plasma processing apparatus comprises: a processing chamber; a source power (SP) coupling element configured to generate plasma in the processing chamber; an SP supply node coupled to the SP coupling element and configured to supply radio frequency (RF) power to the SP coupling element as an SP pulse during an SP pulse duration; a substrate holder disposed in the processing chamber; and a first bias power (BP) supply node coupled to the substrate holder and configured to supply a first DC-biased alternating current (AC) power to the substrate holder as an LBP pulse during a low frequency bias power (LBP) duration that does not overlap with the SP pulse duration, wherein the first DC-biased AC power is less than about 800 kHz and includes a first BP frequency greater than 0 Hz. A plasma processing apparatus comprising a second BP supply node coupled to the substrate holder and configured to supply a second DC-biased AC power as an HBP pulse to the substrate holder during a high frequency bias power (HBP) pulse duration that overlaps with at least a portion of the SP pulse duration, wherein the second DC-biased AC power comprises a second BP frequency greater than 800 kHz. Claim 16 A plasma processing apparatus according to claim 15, wherein the first BP frequency is approximately 400 kHz. Claim 17 A plasma processing apparatus according to claim 16, wherein the second BP frequency is approximately 13 MHz. Claim 18 A plasma processing apparatus according to claim 17, wherein the SP coupling element is a helical resonator disposed outside the processing chamber and configured to generate inductively coupled plasma in the processing chamber, and the RF power includes an RF power frequency equal to about 27 MHz. Claim 19 A plasma processing apparatus according to claim 15, wherein the first BP supply node and the second BP supply node are configured to simultaneously supply the first DC-biased AC power and the second DC-biased AC power to the substrate holder. Claim 20 A plasma processing apparatus according to claim 7, wherein the LBP duration of each LBP pulse supplied by the first BP supply node is less than about 1 μs.

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