Plasma processing method using low frequency bias pulse

Abstract

A plasma processing method includes: supplying a first source power (SP) pulse to a SP coupling element for a first SP pulse duration to generate a plasma in a processing chamber; supplying a high frequency bias power (HBP) pulse to a substrate holder disposed in the processing chamber for a HBP pulse duration that overlaps with the first SP pulse duration; and supplying a first low frequency bias power (LBP) pulse to the 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 approximately 800 kHz.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of the filing date of U.S. patent application Ser. No. 16 / 785,260, filed February 7, 2020, which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to plasma processing, and in particular embodiments to plasma processing methods, apparatus, and systems using low frequency bias pulses. [Background technology]

[0003] Device formation in a microelectronic workpiece can involve a series of manufacturing techniques that include the formation, patterning, and removal of several material layers on a substrate. To achieve the physical and electrical specifications of current and next-generation semiconductor devices, process flows that allow for the reduction of feature dimensions while maintaining structural integrity are desirable for various patterning processes. As device structures become denser and more vertically advanced, the need for precision material processing becomes more acute.

[0004] Plasma processes are commonly used to form devices, interconnects, and contacts in microelectronic workpieces. Plasma processes are used in various processing stages, such as front-end-of-line (FEOL), middle-of-line (MOL), and back-end-of-line (BEOL). For example, plasma etching and plasma deposition are common process steps during semiconductor device fabrication. A combination of source power (SP) applied to a coupling element and bias power (BP) applied to a 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 plasma species. However, conventional plasma processes have struggled to decouple these effects from one another, resulting in loss of process control and precision. Thus, a plasma processing method that decouples the effects of SP and BP may be desirable. Summary of the Invention [Means for solving the problem]

[0005] According to an embodiment of the present invention, a plasma processing method includes: supplying a first SP pulse to an SP coupling element for a first SP pulse duration to generate a plasma in a processing chamber; supplying 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 supplying a first low frequency BP pulse to the 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 higher than 800 kHz. The first low frequency BP pulse includes a low frequency BP pulse frequency lower than about 800 kHz.

[0006] According to another embodiment of the present invention, a plasma processing method includes providing a first SP pulse to an SP coupling element for a first SP pulse duration to generate a plasma in a processing chamber, 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 including a BP pulse frequency less than about 800 kHz and a BP pulse duration less than about 10 μs.

[0007] According to yet another embodiment of the present invention, a plasma processing apparatus includes a processing chamber, an SP coupling element configured to generate a 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 includes a first BP supply node coupled to the substrate holder and configured to supply a first DC bias power to the substrate holder, and a second BP supply node coupled to the substrate holder and configured to supply a second DC bias power to the substrate holder. The first DC bias power includes a first BP frequency less than about 800 kHz. The second DC bias power includes a second BP frequency greater than 800 kHz.

[0008] For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions which should be read in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0009] [Figure 1] 1 shows a schematic timing diagram of an example plasma processing method and corresponding qualitative graphs of the effect of BP pulse frequency and BP pulse duration on coupling, in accordance with an embodiment of the present invention. [Diagram 2] 1 shows a schematic timing diagram of another example plasma processing method according to an embodiment of the present invention, corresponding qualitative graphs of ion density and potential at a substrate, and a schematic diagram of possible effects of high frequency BP pulses at a substrate. [Diagram 3] 4 shows a schematic timing diagram of yet another example plasma processing method, along with corresponding qualitative graphs of ion density and potential at a substrate, in accordance with an embodiment of the present invention; [Figure 4] 1A-1D show schematic timing diagrams of various plasma processing methods according to embodiments of the present invention; [Diagram 5] 1 shows schematic timing diagrams of several plasma processing methods and corresponding qualitative graphs of electron density and ion flux according to embodiments of the present invention. [Figure 6] 1 shows a schematic block diagram of an example plasma processing system, in accordance with an embodiment of the present invention. [Figure 7] 1 illustrates an example plasma processing method according to an embodiment of the present invention. [Figure 8] 4 illustrates another example plasma processing method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The drawings are drawn to clearly show relevant aspects of the embodiments and are not necessarily drawn to scale. The ends of features drawn in the drawings do not necessarily indicate the ends of the range of the features.

[0011] Making and using various embodiments are described in detail below. It should be understood, however, that the various embodiments described herein may be applied in a variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the various embodiments and should not be construed as limiting in scope.

[0012] Control of plasma characteristics can be important when performing plasma processing methods (e.g., plasma etching and plasma deposition). Further control can be achieved by utilizing pulsed techniques that provide source power and bias power to the processing chamber with appropriate timing. Techniques that include SP and / or BP pulses can sometimes be referred to as advanced pulsed 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 periodic pulse sequence of pulses including two or more loosely defined phases. In a first phase (e.g., SP phase or plasma generation phase), an SP pulse may be applied to a coupling element (e.g., a coil of a helical resonator) to generate a high-density plasma including ions and radicals. In a second phase (e.g., BP phase or ion acceleration phase), one or more BP pulses may be applied to a substrate holder to couple energy to the ions and direct them toward a substrate supported by the substrate holder. A third phase in which SP and / or BP are off may be utilized to allow control of by-products in the process chamber (e.g., off phase or by-product management phase).

[0014] The SP can be supplied as alternating current (AC) power in the radio frequency (RF) band (e.g., high frequency (HF), very high frequency (VHF), etc.). The 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 processing methods apply both SP and BP in the HF band. However, the energy imparted to ions in the plasma by the BP pulse may be minimal, even though there is no SP during the BP phase. Even with a BP frequency of 2 MHz (i.e., in the MF band), the bulk of ions reaching the substrate surface may be near thermal equilibrium (i.e., with negligible vertical velocity / large ion angle). For example, a BP frequency above about 645 kHz may increase the plasma electron temperature T e This can increase the ion velocity and generate parasitic plasma during the BP phase. The generation of parasitic plasma can contribute to the lack of ion verticality because a large bias voltage and a large sheath can cause most of the ion energy to be lost in collisions.

[0016] When applying a BP pulse to the substrate holder, the SP coupling element (e.g., an inductive coil) can act as a low-frequency return path for the power coupled to the substrate through the substrate holder. A low-frequency BP pulse can change the structure of the plasma compared to a high-frequency BP pulse. The plasma can be sensitively affected by a small amount of LF power in the coil. For example, an increase in BP can increase the plasma density (e.g., n e ) rises, but n e Both the rise time and fall time of n may decrease. In addition, as SP increases relative to BP, the rise time and fall time may decrease, but e is virtually unaffected.

[0017] Due to the sensitivity of plasma characteristics to the application of BP, a wide range of conditions can cause parasitic plasma to occur, destroying the decoupling between plasma generation and ion acceleration. As BP increases, ion energy (i.e., ion temperature) can also increase undesirably, resulting in an ion density distribution that grows toward the substrate until parasitic plasma occurs at the substrate surface. As a specific example, in a system containing an argon (Ar) plasma with the addition of chlorine (e.g., Cl2), parasitic plasma can occur at a BP voltage of 500 V at 800 kHz.

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

[0019] Embodiments of the plasma processing method advantageously decouple the generation of the plasma from the applied BP. For example, the SP and BP can be advantageously decoupled to enhance control and reduce complexity. In other words, crosstalk between the source and the bias can be reduced or eliminated. The plasma processing methods described herein also advantageously result in a near-vertical ion velocity V ⊥ (i.e., perpendicular / small ion angle to the substrate surface), heating of the plasma (e.g., T e ) or little or no generation and little or no ion heating (i.e., small horizontal / parallel velocities V II ) Thus, the verticality of the ions can be beneficially maintained throughout the BP phase.

[0020] A further advantage may be that a plasma with cold bulk ions is generated, resulting in high density, high pressure, and thin sheath. Advantageously, the plasma processing method described herein may result in little or no plasma generation from the applied BP. Advantageously, a large ion flux can be extracted at the substrate by the BP pulse with a frequency below a certain critical frequency threshold.

[0021] The embodiments presented below describe various plasma processing methods, as well as systems and apparatus for performing plasma processing methods, particularly plasma processing methods including LBP pulses. The following description describes these embodiments. FIG. 1 is used to describe an example schematic timing diagram of an embodiment plasma processing method. FIGS. 2 and 3 are used to describe two example schematic timing diagrams of an embodiment plasma processing method including HBP pulses. FIGS. 4 and 5 are used to describe several additional schematic timing diagrams of embodiment plasma processing methods. FIG. 6 is used to describe an example plasma processing system including an example plasma processing apparatus. FIGS. 7 and 8 are used to describe two example plasma processing methods.

[0022] FIG. 1 shows a schematic timing diagram of an example plasma processing method and corresponding qualitative graphs of the effect of BP pulse frequency and BP pulse duration on coupling, in accordance with an embodiment of the present invention.

[0023] 1, a schematic timing diagram 100 illustrates the application of SP and BP in 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, the SP is AC power, and in some embodiments, it is RF power. Thus, each SP pulse 112 has an SP pulse frequency f , which indicates the frequency of the applied power. S For example, the SP pulse frequency f S may be in the HF band, the VHF band, etc. In one embodiment, the SP pulse frequency f S In another embodiment, the SP pulse frequency f S is about 13MHz.

[0024] Similarly, the BP may be AC ​​power (e.g., DC biased AC power) or DC power. Each LBP pulse 122 has an LBP pulse frequency f less than about 800 kHz. LIncludes the LBP pulse frequency f L may be in the MF, LF, VLF, or lower bands. For example, the LBP pulse frequency f L may be zero, corresponding to a continuous wave (CW) DC power. In addition, the BP delivered as DC power may be bipolar to counteract charging effects at the substrate. In some embodiments, the LBP pulse frequency f L The LBP pulse frequency f is less than about 645 kHz, and in one embodiment is about 400 kHz. L SP pulse frequency f S There are no foreseeable limitations.

[0025] As an indication of the duration of each type of pulse, each SP pulse 112 is designated by an SP pulse duration t S Each LBP pulse 122 has an LBP pulse duration t L As shown in the figure, the SP pulse duration t S and LBP pulse duration t L In various embodiments, the LBP pulse duration t L The SP pulse duration t is less than about 100 μs, and in one embodiment is about 80 μs. S and LBP pulse duration t L In other words, there is no required relationship between the LBP pulse duration t L is the SP pulse duration t depending on the specific details of a given plasma process. S may be longer than the SP pulse duration t S or the SP pulse duration t S It may be shorter than that.

[0026] By combining appropriate timing between the SP and LBP pulses with a low frequency of the LBP pulse, the effect of the applied SP can be advantageously decoupled from the effect of the applied BP, for example, in the optimum region 11, the effect of BP on plasma generation can be reduced or eliminated, as shown in the qualitative graph 101 of BP pulse frequency versus BP pulse duration.

[0027] The optimum region 11 corresponds to the case where the values ​​of the BP pulse frequency and the BP pulse duration are sufficiently small. In particular, for a certain critical BP pulse frequency f C Above this threshold, strong coupling exists and may result in undesirable secondary plasma generation. For example, when a BP of 13.56 MHz is applied, a secondary plasma is generated above the wafer, which may result in a change in the radical-to-ion ratio, which may, among other things, change the degree and / or selectivity of sidewall passivation. C Although the specific value of may depend on various factors, the critical BP pulse frequency f C can be about 645 kHz. For example, a BP pulse (e.g., impulse bias) delivered as DC power at 645 kHz may not result in additional plasma generation and may not perturb the plasma or corresponding afterglow generated by a previous SP pulse.

[0028] Similarly, for a particular critical BP pulse duration t C A BP pulse duration exceeding t can form strong couplings that can lead to undesirable changes in the plasma structure. For example, a possible drawback of a long duration is that the plasma can begin to decay, which can change the structure of the plasma. C The specific value of may also depend on several factors and may be, for example, about 25 μs to about 300 μs. C One factor that can affect the specific value of is the difference between the electron temperature T e There is a speed at which the T by BP changes. e If the rise of t is slow, C The value of can be large.

[0029] Therefore, to stay in the optimum region and avoid the strong coupling scenario, the critical BP pulse frequency f C LBP pulse frequency f L , and the critical BP pulse duration t C LBP pulse duration t LFor example, in some cases, an LBP pulse having an LBP pulse frequency f of about 400 kHz is applied. L is the plasma generation or electron temperature T e This is a desirable frequency because it can be well decoupled from the rise in . However, although not required, an HBP pulse may also be suitably combined with an LBP pulse, as described below, while maintaining weak or no coupling.

[0030] 2 shows a schematic timing diagram of another example plasma processing method, corresponding qualitative graphs of ion density and potential at a substrate, and a schematic diagram of the effect of an HBP pulse that may occur at a substrate, according to an embodiment of the present invention. The schematic timing diagram of FIG. 2 may be a specific implementation of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1. Similarly labeled elements may be as described above.

[0031] 2, a schematic timing diagram 200 illustrates the application of SP and BP in a plasma processing system. The SP pulse frequency f S and SP pulse duration t S and an SP pulse 212 having an LBP pulse frequency f L and LBP pulse duration t L A LBP pulse 222 having a pulse period of 1 ms is provided to the plasma processing system. Specifically, the pulse period 209 may be periodically performed multiple times to perform the plasma processing method of a given embodiment. The pulse period 209 may have any suitable duration, and in one embodiment is about 1 ms.

[0032] The pulse period 209 may be conceptually divided into several phases, such as three phases as shown. An SP pulse 212 is applied to the plasma processing system in phase 201, and an LBP pulse 222 is applied in phase 202. Phase 201 may be referred to as the SP phase or plasma generation phase. Phase 202 may be referred to as the BP phase or ion acceleration phase. Optionally, phase 203 may also be included as shown, during which the SP and BP are turned off. Phase 203 may be referred to as the off phase or by-product management phase.

[0033] In addition, HBP pulses 232 are also provided in phase 201. The HBP pulses 232 have an HBP pulse frequency f H and HBP pulse duration t H As shown, the HBP pulse duration t H is the SP pulse duration t S Alternatively, the HBP pulse duration t H is the SP pulse duration t S Additionally or alternatively, the HBP pulse 232 may also be applied in other phases, as described below. For example, the HBP pulse 232 may also be applied in phase 202. The HBP pulse frequency f H is the LBP pulse frequency f L For example, in various embodiments, f L is lower than about 800kHz, and f H In some embodiments, f is greater than 800 kHz. H is in the HF band, which in one embodiment is approximately 13.56 MHz.

[0034] The pulse has an ion density of n i and the root-mean-square potential V on the substrate rms For example, as shown in qualitative graph 205, the ion density n iSince the LBP pulse 222 is decoupled from the plasma being generated, the ion density n i decreases, which may correspond to an afterglow. In contrast, the potential at the substrate V rms is relatively low and constant in phase 201, but increases in phase 202 due to the application of the LBP pulse 222. Following the afterglow, the ion density n i continues to decrease gradually, while the potential V rms drops rapidly to near zero during the phase 203 with no power applied.

[0035] The pulse timing illustrated in schematic timing diagram 200 may be advantageously used in several plasma processing methods (e.g., plasma processing methods for logic fabrication), such as thin etching, profile etching (e.g., managing thin top and bottom corner rounding), and patterning (e.g., silicon nitride, silicon oxide, silicon), as well as multiple patterning applications.

[0036] The HBP pulse may be desirable to modify the radical generation rate (e.g., Cl) and / or to affect the etching profile. The HBP pulse may also be advantageously used to control the cleanliness of a given plasma process (e.g., during SP application in a reverse phase process). For example, the HBP pulse may be used to control the passivation of horizontal surfaces. Referring now to schematic 206, a mask 55 may delineate the etching area of ​​a substrate 256, including 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. The passivation layer 57 is an oxide film in some embodiments. Although an oxide film may be beneficial for protecting the sidewalls, it may risk reducing the etch rate and stopping the etch if it forms on the horizontal surfaces. As shown in schematic 206, the HBP pulse 232 in phase 201 may reduce or prevent the passivation layer 57 from forming on the horizontal surfaces of the substrate 256, which may advantageously help manage the etch front.

[0037] In phase 202, the HBP pulse 232 is off and the LBP pulse 222 is on. Different BP frequencies in different phases in a given plasma process may be beneficial. For example, in some cases, it may be advantageous to provide a pure low frequency BP in the bias phase to facilitate improved decoupling. However, the HBP pulse 232 may also extend into and span both phases 202 and 203. Similarly, providing a high frequency BP in the source phase may advantageously control surface interactions at the substrate surface (e.g., by suppressing oxide formation on horizontal surfaces such as the bottom of a feature). For example, applying HBP together with SP may allow LBP (e.g., 400 kHz) to reduce the V of the afterglow. PP While maximizing the potential (plasma potential V PP and DC potential V DC) can be maintained. Also, as mentioned above, the HBP pulse can be omitted (eg, if control of the potential at the substrate is less important in the source phase).

[0038] One specific implementation of the plasma processing method illustrated with the schematic timing diagram 200 can be silicon (Si) etching using a 50:50 mixture of HBr and Ar with the addition of CF4 and O2. In this specific example, the SP pulse 212 has a pulse duration of t S is about 20μs, and f S In the HF band (e.g., 13.56 MHz, 26 MHz, etc.), the SP pulse power P of about 500 W S The HBP pulse 232 may be applied at f H is approximately 13.56 MHz, and is of the same duration (t H = 20μs), the HBP pulse power P of about 100W H The LBP pulse 222 can be applied at f L is about 400 kHz, and the longer duration (t L = 80μs), the LBP pulse power P of about 500W L Phase 203 may be implemented as an off phase to control by-products and may have a duration of about 900 μs. Thus, in this specific example, the duration of pulse period 209 may be about 1 ms.

[0039] 3 shows a schematic timing diagram of yet another example plasma processing method, and corresponding qualitative graphs of ion density and potential at a substrate, according to an embodiment of the present invention. The schematic timing diagram of FIG. 3 may be a specific implementation of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1. Similarly labeled elements may be as described above.

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

[0041] Qualitative graph 305 shows how the extended duration of the HBP pulse 332 increases the ion density n i and the potential at the substrate V rms As shown, the effect of i and V rms In phases 301 and 302, n behaves similarly to the corresponding phases 201 and 202 in FIG. i and V rms Both are held at relatively constant non-zero values ​​by the HBP pulse 332. i and V rms ion density n i can be maintained at a desired level corresponding to a low density plasma by the HBP pulse 332 of phase 303. This “tickle” plasma can advantageously allow for easy ignition immediately after phase 303.

[0042] Additionally, note that in this case, the HBP pulse 332 may be maintained throughout phase 302, resulting in increased ion flux in this phase. However, the HBP may also potentially be switched off in phase 302. Whether or not the HBP pulse can be maintained in phase 302 may depend on the impact of by-product redeposition on a given process.

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

[0044] 4, several schematic timing diagrams show a non-exhaustive sampling of scenarios for SP, HBP, and LBP timing and power in various plasma processing methods. Each of diagrams (a)-(i) includes at least one SP pulse 412 and an LBP pulse 422, and is conceptually divided into three phases (phase 1, phase 2, and phase 3). The diagrams differ from each other in that various HBP pulses having various durations and timings and additional SP pulses may also be included.

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

[0046] Similarly, diagram (d) illustrates a similar scenario to that of Fig. 2, where an HBP pulse 432 is applied simultaneously with the SP pulse 412, but in addition an additional HBP pulse 436 is applied simultaneously with the LBP pulse 422. Thus, the timing scenario illustrated in diagram (d) is similar to that of diagram (c), except with an interval between the SP pulse 412 and the LBP pulse 422 where the HBP is off. In diagram (d), the HBP pulse 432 and the additional HBP pulse 436 are shown as having the same power. However, this need not be the case. For example, as shown in diagram (e), a low power HBP pulse 437 may be provided during the LBP pulse 422.

[0047] Diagram (f) illustrates a similar scenario to that of diagram (a), but now with a low power SP pulse 416. For example, the SP pulse 412 has a first SP pulse power P of about 500 W. S1 while the low power SP pulse 416 may have a second SP pulse power P of about 100 W. S2 P S1 and P S2 Any relationship may be used and may depend on the specific requirements of a given plasma processing method. For example, S1 For P S2 A lower power of the SP may be used to provide a small amount of additional plasma. Additionally, as shown in (g), (h), and (i), continuous low power SP pulses 417 may be applied throughout both phases 2 and 3. Turning on the SP in phase 3 may reduce ion density and increase ion flux, which may be desirable in some cases.

[0048] Also note that although there may be no delay as shown, in practice there may be a delay between the SP pulse 412 and the low power SP pulse 416. For example, the delay may be about 5 μs or other values. 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 Figure 4, any suitable combination of these and other embodiments described herein, including at least one SP pulse and at least one LBP pulse, may be made to meet the specific needs of a particular application of the invention. Although the HBP pulse is shown to begin simultaneously with the SP pulse or the LBP pulse, this need not be the case. In other words, the start of any of the illustrated HBP pulses may be offset in time relative to the SP pulse or the LBP pulse, similar to offsetting the timing of the end of the HBP pulse illustrated in Figure 4.

[0050] 5 shows schematic timing diagrams of several plasma processing methods according to embodiments of the present invention, as well as corresponding qualitative graphs of electron density and ion flux. The schematic timing diagram of FIG. 5 may be a specific implementation of other schematic timing diagrams described herein, such as the schematic timing diagram of FIG. 1. Similarly labeled elements may be as described above.

[0051] Referring to Figure 5, a schematic timing diagram 501 shows the application of a SP pulse 512 without the application of a BP. e and the corresponding qualitative graph of ion flux is e and ion flux is high during the SP pulse 512 and then decreases after the SP ends. The ion flux decreases rapidly, n e As shown in schematic timing diagram 502, the LBP pulse duration tL By introducing an LBP pulse 522 at e The rate at which t decreases can vary. L A sufficiently long LBP pulse 522 may perturb the plasma so that it decays faster. For example, the ion flux may reflect the background plasma density. However, it may be desirable to generate more ion flux (e.g., dose) before applying the next SP pulse.

[0052] For example, a sufficiently short LBP pulse can affect the ion flux without strongly perturbing the background plasma. In other words, the impulse bias picks up the flux but does not perturb the afterglow. This can be seen in schematic timing diagram 503, which shows that a sufficiently short LBP pulse (i.e., LBP spike 526) can affect the ion flux without strongly perturbing the background plasma. e , while not affecting n, while producing a corresponding sharp peak in the ion flux. As shown, the LBP spike 526 increases the ion flux while also increasing the background plasma (i.e., n e ) with LBP spike duration t short enough to have minimal or no effect on k In various embodiments, t K is less than 20 μs, and in some embodiments, less than 10 μs. K In another embodiment, t K is approximately 1 μs.

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

[0054] Long LBP pulses may result in parasitic plasma generation and / or changes in plasma structure, as described above. In a BP "pulse train", however, parasitic plasma generation may increase more slowly. Thus, as shown in schematic timing diagram 504, multiple appropriately spaced LBP spikes 526 may advantageously produce a relatively constant ion flux without diminishing afterglow. For example, a dose train at energies (e.g., gradually increasing with decreasing background density) may advantageously result in a more monoenergetic beam.

[0055] Interval between adjacent LBP spikes 526 D is, inter alia, the frequency of the applied BP and t K However, the length of t D should be adjusted to avoid background plasma fluctuations (e.g., electron temperature T e For example, in various embodiments, t D is K In some embodiments, t D In another embodiment, t D is about 10 μs to about 50 μs.

[0056] In some cases, surface charging may be an issue when applying LBP pulses and / or LBP spikes (e.g., dielectric substrates, etc.). The magnitude of the charging effect may depend on the materials contained in a 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 undesired charging effect by using bipolar DC power for the LBP spikes 526. For example, every other LBP spike may be made positive, or other patterns such as ----+++, --+, etc. may be used. 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, no limitation is intended on the number of LBP spikes 526. The number of LBP spikes 526 per cycle may depend on the pulse cycle time, dose requirements, and other considerations specific to a given application.

[0057] In addition to multiple LBP spikes 526, an HBP pulse 532 may also be incorporated to facilitate chemistry control when the SP is on, as shown in schematic timing diagram 505. As shown, the ion flux during the SP pulse 512 may be minimally affected by the potential introduced by the HBP pulse 532. This scenario allows the benefits of the HBP power described above to be combined with the benefits of the LBP spike. It should be noted that the LBP spike may be incorporated into any of the timing configurations described above. In other words, the scope of the present invention is intended to include the LBP spike as an optional implementation for any LBP pulse described herein.

[0058] FIG 6 shows a schematic block diagram of an example 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 plasma processing method embodiments described herein, such as the schematic timing diagrams of FIG 1-FIG 5. Furthermore, the plasma processing system and plasma processing apparatus of FIG 6 may be used to perform any of the method embodiments described herein, such as the plasma processing methods of FIG 7 and FIG 8.

[0059] 6, a plasma processing system 600 includes a plasma processing apparatus 50 with an SP coupling element 60 (e.g., an inductive coil, a helical resonator, etc.) coupled to a processing chamber 54. Although the SP coupling element 60 is shown as an inductive coil disposed outside the quartz window 52 of the plasma processing apparatus 50, the SP coupling element 60 may also be implemented as a conductive plate inside the processing chamber 54 or other suitable configurations (e.g., an antenna, an electrode, a waveguide, an electron beam, etc.). The SP coupling element 60 is configured to couple SPs to the processing chamber 54 to generate a plasma 58 inside the processing chamber 54. The plasma 58 may be any type of plasma, such as an inductively coupled plasma (ICP), a capacitively coupled plasma (CCP), a surface wave plasma (SWP), etc.

[0060] A substrate holder 70 (e.g., an electrostatic chuck) is disposed within the process chamber 54. The substrate holder 70 is configured to support a substrate 656. The substrate holder 70 is further configured to couple a BP to the process chamber 54. The coupled BP may include both an HBP and an LBP, as described herein.

[0061] The SP may be supplied to the process chamber 54 using an SP control path that includes an SP supply node 62 coupled to an SP coupling element 60 and an SP controller 64. The SP supply node 62 may also be coupled to or include a waveform generator. In addition, the SP supply node 62 and the SP controller 64 may be combined. An optional 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 process chamber 54 using separate or combined BP control paths including HBP supply node 72 and LBP supply node 82 coupled to the substrate holder 70 and to HBP controller 74 and LBP controller 84 as shown. As with SP, either or both of the HBP supply node 72 and LBP supply node 82 may also be coupled to or comprise respective waveform generators. Also as above, an optional HBP matching stage 75 and / or an optional LBP matching stage 85 may be included between the substrate holder 70 and the corresponding supply node. In some cases (e.g., for bipolar DCLBP pulses / spikes), the LBP supply node 82 may be split 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 described above. The SP, HBP, and LBP pulses may be in phase, overlap, or out of phase with each other.

[0064] 7 illustrates an example plasma processing method according to an embodiment of the present invention. The plasma processing method of FIG. 7 may be performed using the schematic timing diagrams and plasma processing systems and apparatuses according to the embodiments described herein. For example, the plasma processing method of FIG. 7 may be combined with any of the embodiments of FIG. 1-FIG. 6. The following method steps may be performed in any suitable order, as would be apparent to one of ordinary skill in the art.

[0065] 7, step 701 of a plasma processing method 700 includes providing an SP pulse to an SP coupling element for an SP pulse duration to generate a plasma in a processing chamber. Step 702 includes providing an HBP pulse to a substrate holder disposed 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 includes 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 example plasma processing method according to an embodiment of the present invention. The plasma processing method of FIG. 8 may be performed using the schematic timing diagrams and plasma processing systems and apparatuses of the embodiments described herein. For example, the plasma processing method of FIG. 8 may be combined with any of the embodiments of FIG. 1-FIG. 6. Furthermore, the plasma processing method of FIG. 8 is not intended to be mutually exclusive with other plasma processing methods described herein. For example, the plasma processing method of FIG. 8 may be combined with the plasma processing method of FIG. 7. The steps of the following methods may be performed in any suitable order, as would be apparent to one of ordinary skill in the art.

[0067] 8, step 801 of a plasma processing method 800 includes providing an SP pulse to an SP coupling element for an SP pulse duration to generate a plasma in a processing chamber. Step 802 includes providing a plurality of BP pulses to a substrate holder disposed in the processing chamber for BP pulse durations that do not overlap with the SP pulse duration. Each of the plurality of BP pulses has a BP pulse frequency less than about 800 kHz and a BP pulse duration less than about 10 μs.

[0068] Exemplary embodiments of the present invention are summarized here. Other embodiments can be seen throughout the specification and claims appended hereto. EXAMPLES

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

[0070] Example 2. The plasma processing method of example 1, wherein the HBP pulse duration completely overlaps both the first SP pulse duration and the first LBP pulse duration.

[0071] Example 3. The plasma processing method of example 1, wherein the HBP pulse duration completely overlaps with and is equal to the first SP pulse duration.

[0072] Example 4. The plasma processing method of any one of Examples 1-3, further comprising: after the first SP pulse duration, supplying a second SP pulse to the SP coupling element for a second SP pulse duration that overlaps with the first LBP pulse duration, wherein the first SP pulse comprises a first SP pulse power and the second SP pulse comprises a second SP pulse power that is less than the first SP pulse power.

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

[0074] Example 6. The plasma processing method of any one of Examples 1-5, further comprising: after the first LBP pulse duration, supplying a second SP pulse to the SP coupling element for a second SP pulse duration; and supplying a second LBP pulse to the substrate holder for a second LBP pulse duration that does not overlap with the second SP pulse duration.

[0075] Example 7. The plasma processing method of example 6, further comprising: after the first LBP pulse duration, not supplying SP to the SP coupling element and not supplying LBP to the substrate holder for a delay duration, and a second SP pulse is supplied after the delay duration.

[0076] Example 8. The plasma processing method of example 7, wherein the HBP pulse duration completely overlaps the first SP pulse duration and the first LBP pulse duration and at least partially overlaps the delay duration, and the HBP pulse comprises an HBP power that is less than the LBP pulse power of the first LBP pulse.

[0077] Example 9. A plasma processing method comprising: supplying a first SP pulse to a source power (SP) coupling element for a first SP pulse duration to generate a plasma in a processing chamber; and supplying 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, each of the plurality of BP pulses comprising a BP pulse frequency less than about 800 kHz and a BP pulse duration less than about 10 μs.

[0078] Example 10. The plasma processing method of example 9, further comprising: supplying a high frequency bias power (HBP) pulse to the substrate holder for a second BP pulse duration that overlaps with the SP pulse duration, the HBP pulse comprising a frequency greater than 800 kHz.

[0079] Example 11. The plasma treatment method of example 10, wherein the second BP pulse duration completely overlaps with and is equal to the SP pulse duration.

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

[0081] Example 13. The plasma processing method according to any one of Examples 9 to 12, wherein each of the multiple BP pulses is a single direct current (DC) pulse.

[0082] Example 14. The plasma treatment method of example 13, wherein a portion of the plurality of BP pulses are positive DC pulses and a remaining portion of the plurality of BP pulses are negative DC pulses.

[0083] Example 15. The plasma processing method of any one of Examples 9-14, wherein each of the plurality of BP pulses comprises a BP pulse duration 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 a 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 direct current (DC) bias power to the substrate holder, the first DC bias power having a first BP frequency less than about 800 kHz; and a second BP supply node coupled to the substrate holder and configured to supply a second DC bias power to the substrate holder, the second DC bias power having a second BP frequency greater than 800 kHz.

[0085] Example 17. The plasma processing apparatus of Example 16, wherein the first BP frequency is about 400 kHz.

[0086] Example 18. The plasma processing apparatus according to Example 16 or 17, wherein the second BP frequency is about 13 MHz.

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

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

[0089] While the present invention has been described with reference to exemplary embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of those exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any such modifications or embodiments.

Claims

1. providing a first SP pulse to a source power coupling element (SP coupling element) for a first SP pulse duration to generate a plasma in the processing chamber; providing a radio frequency bias power pulse duration (HBP pulse duration) to a substrate holder disposed in the process chamber that overlaps with at least a portion of the first SP pulse duration, the HBP pulse comprising an HBP pulse frequency greater than 800 kHz; providing a first LBP pulse to the substrate holder for a first low frequency bias power pulse duration (first LBP pulse duration) that does not overlap with the first SP pulse duration, the first LBP pulse comprising an LBP frequency less than 800 kHz; A plasma processing method comprising:

2. 2. The plasma processing method of claim 1, wherein the HBP pulse duration completely overlaps both the first SP pulse duration and the first LBP pulse duration.

3. 2. The plasma processing method of claim 1, wherein the HBP pulse duration completely overlaps and is equal to the first SP pulse duration.

4. providing a second SP pulse to the SP coupling element after the first SP pulse duration for a second SP pulse duration that overlaps with at least a portion of the first LBP pulse duration; the first SP pulse comprises a first SP pulse power; the second SP pulse includes a second SP pulse power that is less than the first SP pulse power; The plasma processing method of claim 1 , further comprising:

5. 2. The plasma processing method of claim 1, wherein the first SP pulse duration is 20 μs and the first LBP pulse duration is 80 μs.

6. providing a first SP pulse to a source power coupling element (SP coupling element) for a first SP pulse duration to generate a plasma in the processing chamber; providing a plurality of BP pulses to a substrate holder disposed in the process chamber for a first bias power pulse duration (first BP pulse duration) that does not overlap with the first SP pulse duration, each of the plurality of BP pulses comprising a BP pulse frequency less than 800 kHz and a BP pulse duration less than 10 μs; A plasma processing method comprising:

7. providing a radio frequency bias power pulse (HBP pulse) to the substrate holder for a second BP pulse duration overlapping with the first SP pulse duration, the HBP pulse including a frequency greater than 800 kHz; The plasma processing method of claim 6 , further comprising:

8. 8. The plasma processing method of claim 7, wherein the second BP pulse duration completely overlaps and is equal to the first SP pulse duration.

9. The plasma processing method of claim 6 , wherein each of the plurality of BP pulses is a single direct current pulse (DC pulse).

10. 10. The plasma processing method of claim 9, wherein a portion of the plurality of BP pulses are positive DC pulses and a remaining portion of the plurality of BP pulses are negative DC pulses.

11. The plasma processing method of claim 6 , wherein each of the plurality of BP pulses comprises a BP pulse duration less than 1 μs.

12. A plasma processing apparatus configured to carry out the method of any one of claims 1 to 11, comprising: a processing chamber; a source power coupling element (SP coupling element) configured to generate a 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 supply node (first BP supply node) coupled to the substrate holder and configured to supply a first direct current bias power (first DC bias power) to the substrate holder, the first DC bias power including a first BP frequency lower than 800 kHz; a second BP supply node coupled to the substrate holder and configured to supply a second DC bias power to the substrate holder, the second DC bias power comprising a second BP frequency greater than 800 kHz; A plasma processing apparatus comprising:

13. The plasma processing apparatus of claim 12 , wherein the first BP frequency is 400 kHz.

14. The plasma processing apparatus of claim 13 , wherein the second BP frequency is 13 MHz.

15. the SP coupling element is a helical resonator disposed outside the processing chamber and configured to generate an inductively coupled plasma in the processing chamber; The plasma processing apparatus of claim 14 , wherein the RF power comprises an RF power frequency equal to 27 MHz.

16. The plasma processing apparatus of claim 12 , wherein the first BP supply node and the second BP supply node are configured to simultaneously supply the first DC bias power and the second DC bias power to the substrate holder.

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