Plasma processing method using low frequency bias pulses

Abstract

A method of plasma processing includes providing a first source power (SP) pulse to an SP coupling element for a first SP pulse duration to generate a 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 overlapping the first SP pulse duration, and providing a first low frequency bias power (LBP) pulse to the substrate holder for a first LBP pulse duration not overlapping 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

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. non-provisional patent application No. 16 / 785,260, filed on February 7, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention generally relates to plasma processing, and in specific embodiments, to plasma processing methods, apparatus and systems using low-frequency bias pulses. Background Technology

[0004] Device fabrication within microelectronic workpieces can involve a range of manufacturing 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, it is desirable to reduce the fabrication process size while maintaining structural integrity for various patterning processes. With the increasing densification and vertical integration of device structures, the demand for precision material processing is becoming increasingly urgent.

[0005] 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 online (FEOL), mid-end online (MOL), and back-end online (BEOL). For example, plasma etching and plasma deposition are common process steps during semiconductor device fabrication. A combination of source power (SP) applied to the coupling element and bias power (BP) applied to the substrate holder can be used to generate and guide plasma. SP can be used to generate plasma, thereby increasing the plasma temperature. Similarly, BP can be used to impart velocity to the plasma material. However, conventional plasma processes struggle to separate these effects from each other, leading to reduced process control and precision. Therefore, plasma processing methods that separate the effects of SP and BP may be desirable. Summary of the Invention

[0006] According to an embodiment of the present invention, a plasma processing method includes: providing a first SP pulse to an SP coupling element during a first SP pulse duration to generate plasma in a processing chamber; providing a high-frequency BP pulse to a substrate holder disposed in the processing chamber during a high-frequency BP pulse duration overlapping with the first SP pulse duration; and providing a first low-frequency BP pulse to the substrate holder during a first low-frequency BP pulse duration not overlapping 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.

[0007] According to another embodiment of the present invention, a plasma processing method includes: providing a first SP pulse to an SP coupling element during a first SP pulse duration to generate plasma in a processing chamber; and providing a plurality of BP pulses to a substrate holder disposed in the processing chamber during 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.

[0008] According to another embodiment of the present invention, a plasma processing apparatus includes: a processing chamber; an SP coupling element configured to generate plasma within 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 within 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. Attached Figure Description

[0009] To gain a more complete understanding of the invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 A schematic timing diagram of an example plasma processing method according to an embodiment of the present invention is shown, along with corresponding qualitative curves illustrating the effects of BP pulse frequency and BP pulse duration on coupling.

[0011] Figure 2 A schematic timing diagram of another example plasma processing method according to an embodiment of the present invention, a corresponding qualitative curve of ion density and potential at the substrate, and a schematic diagram of the possible effects of a higher frequency BP pulse at the substrate are shown.

[0012] Figure 3 A schematic timing diagram of yet another example plasma processing method according to an embodiment of the present invention, and corresponding qualitative curves of ion density and potential at the substrate are shown.

[0013] Figure 4 Schematic timing diagrams of various plasma processing methods according to embodiments of the present invention are shown;

[0014] Figure 5Schematic timing diagrams of several plasma processing methods according to embodiments of the present invention, as well as corresponding qualitative curves of electron density and ion flux, are shown.

[0015] Figure 6 A schematic block diagram of an example plasma processing system according to an embodiment of the present invention is shown;

[0016] Figure 7 An example plasma processing method according to an embodiment of the present invention is shown; and

[0017] Figure 8 Another example plasma processing method according to an embodiment of the present invention is shown.

[0018] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. Figures are drawn to clearly illustrate relevant aspects of the embodiments, and these figures are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate the termination of a feature range. Detailed Implementation

[0019] The following sections discuss in detail the making and use of various embodiments. However, it should be understood that the various embodiments described herein can be applied to a wide variety of specific situations. The specific embodiments discussed are merely illustrative of specific ways of making and using the various embodiments and should not be interpreted in a limited manner.

[0020] When implementing plasma processing methods (e.g., plasma etching and plasma deposition), control of plasma characteristics can be important. Additional control can be achieved by utilizing pulse techniques to provide source power and bias power to the processing chamber at appropriate timing. Techniques including SP pulses and / or BP pulses are sometimes 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.

[0021] Specifically, for example, the APT can be implemented as a cyclic pulse sequence comprising two or more loosely defined phases. During the first phase (e.g., the SP phase or plasma generation phase), SP pulses can 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 the second phase (e.g., the BP phase or ion acceleration phase), one or more BP pulses can be applied to a substrate holder to couple energy to ions and direct them toward the substrate supported by the substrate holder. A third phase can be utilized, in which the SP and / or BP are turned off to allow control of byproducts within the processing chamber (e.g., a shutdown phase or byproduct management phase).

[0022] SP can be supplied as AC power (e.g., high frequency (HF), very high frequency (VHF), etc.) in the radio frequency (RF) range. BP can be supplied as DC power (e.g., continuous DC power, pulsed DC power, bipolar DC power, etc.) or AC power (e.g., HF, intermediate frequency (MF), low frequency (LF), very low frequency (VLF), etc.).

[0023] Traditional plasma processing methods utilize both SP and BP pulses in the HF range. However, although SP is absent during the BP phase, the energy imparted to ions in the plasma by the BP pulse can be minimal. Even at BP frequencies of 2 MHz (i.e., in the MF range), most ions reaching the substrate surface are likely to be near-thermal (i.e., with negligible vertical velocity / large ion angle). For example, BP frequencies above approximately 645 kHz may increase the electron temperature T of the plasma. e This leads to the generation of parasitic plasma during the BP phase. The generation of parasitic plasma may result in a lack of ion verticality, as the large bias voltage and large sheath may cause most of the ion energy to be lost due to collisions.

[0024] When a BP pulse is applied to the substrate holder, the SP coupling element (e.g., an induction coil) can serve as a low-frequency loop for power coupled to the substrate through the substrate holder. Lower-frequency BP pulses may alter the plasma structure compared to higher-frequency BP pulses. Even small amounts of LF power in the coil can sensitively affect the plasma. For example, with increasing BP, the plasma density (e.g., n) will change. e ) may increase, while n e The rise and fall times will decrease. Additionally, as SP increases relative to BP, the rise and fall times may decrease, while n... e It is basically unaffected.

[0025] Due to the sensitivity of plasma properties to the application of BP, a wide range of conditions can generate parasitic plasmas and disrupt the separation between plasma generation and ion acceleration. With increasing BP, the ion energy (i.e., ion temperature) may also undesirably increase, causing the ion density distribution to grow towards the substrate until parasitic plasmas are generated at the substrate surface. As a specific example, in a system containing argon (Ar) plasma with a chlorine (e.g., Cl2) additive, parasitic plasmas can be generated at 800 kHz with a BP voltage of 500 V.

[0026] In various embodiments, the plasma processing method described herein includes providing SP and BP pulses 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 low-frequency BP (LBP) pulse may be applied to a substrate holder. For example, the LBP pulse may have a frequency 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, such as, for example, about 13 MHz. Each LBP pulse may optionally be applied as a plurality of short-duration BP pulses provided after the SP pulse. For example, the duration of each of these plurality of BP pulses may be less than, for example, about 10 μs.

[0027] The plasma processing method described herein can advantageously separate plasma generation from the applied bias (BP). For example, the SP can be advantageously separated from the BP to enhance control and reduce complexity. In other words, crosstalk between the source and the bias can be reduced or eliminated. The plasma processing method described herein can also advantageously generate substantially perpendicular ion velocities V. ⊥ (i.e., perpendicular to the substrate surface / small ion angle), little or no plasma heating (e.g., T) e ) or generation, and little or no ion heating (i.e., small horizontal / parallel velocity V) || Therefore, ion verticality can be beneficially maintained throughout the BP phase.

[0028] Another advantage is the generation of plasma with cold bulk ions, resulting in high density, high pressure, and a thin sheath. Advantageously, in the plasma processing method described herein, the applied BP may generate little or no plasma. BP pulses with frequencies below a certain critical frequency threshold can advantageously extract a large ion flux at the substrate.

[0029] The embodiments provided below describe various plasma processing methods, as well as systems and apparatus for performing these plasma processing methods (particularly plasma processing methods including LBP pulses). The following description illustrates embodiments. Figure 1 An example schematic timing diagram of the plasma processing method of the embodiment is described. Using Figure 2 and Figure 3 Two example schematic timing diagrams of plasma processing methods incorporating HBP pulses are described. Using... Figure 4 and Figure 5 Several additional schematic timing diagrams of the plasma processing method of the embodiments are described. Using Figure 6 This describes an example plasma processing system that includes an example plasma processing apparatus. Using... Figure 7 and Figure 8Two example plasma processing methods are described.

[0030] Figure 1 A schematic timing diagram of an example plasma processing method according to an embodiment of the present invention is shown, along with corresponding qualitative curves illustrating the effects of BP pulse frequency and BP pulse duration on coupling.

[0031] refer to Figure 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, SP is AC power and in some embodiments, it is RF power. Accordingly, each SP pulse 112 has an SP pulse frequency f that indicates the frequency of the applied power. S For example, the SP pulse frequency f S It can be within the HF range, VHF range, etc. In one embodiment, the SP pulse frequency f S Approximately 26MHz. In another embodiment, the SP pulse frequency f S It is approximately 13MHz.

[0032] Similarly, BP can be AC ​​power (e.g., DC bias) or DC power. Each LBP pulse 122 has an LBP pulse frequency f of less than approximately 800 kHz. L LBP pulse frequency f L It can be within the MF range, LF range, VLF range, and even lower. For example, the LBP pulse frequency f L It can be zero, corresponding to continuous wave (CW) DC power. Alternatively, the BP, as the DC power transfer, can be bipolar to counteract the charging effect at the substrate. In some embodiments, the LBP pulse frequency f... L Less than approximately 645 kHz, and in one embodiment approximately 400 kHz. SP pulse frequency f S Relative to the LBP pulse frequency f L There were no anticipated restrictions.

[0033] Each SP pulse 112 has an SP pulse duration t S Each LBP pulse 122 has an LBP pulse duration t that indicates the duration of each type of pulse. L As shown in the figure, the duration t of the SP pulse S and LBP pulse duration t L They do not overlap in time. In various embodiments, the LBP pulse duration t L Less than approximately 100 μs, and in one embodiment approximately 80 μs. SP pulse duration t SWith LBP pulse duration t L There is no necessary relationship between them. In other words, the LBP pulse duration t depends on the specific details of a given plasma process. L It can be greater than, equal to or less than the SP pulse duration t S .

[0034] The appropriate timing between the SP pulse and the LBP pulse, combined with a lower frequency of the LBP pulse, can advantageously separate the effects of the applied SP from those of the applied BP. For example, the effect of BP on plasma generation can be reduced or eliminated in the optimal region 11, as shown in the qualitative curve 101 of BP pulse frequency versus BP pulse duration.

[0035] The optimal region 11 corresponds to sufficiently low BP pulse frequency and BP pulse duration values. Specifically, at a certain critical BP pulse frequency f... C Strong coupling may exist above this, leading to undesirable secondary plasma generation. For example, applying a 13.56 MHz BP pulse can generate secondary plasma above the wafer, which can alter the radical-to-ion ratio, thereby changing the passivation of the sidewalls and / or the selectivity, among other effects. Although the critical BP pulse frequency f... C The specific value may depend on a variety of factors, but the critical BP pulse frequency f C It can be approximately 645 kHz. For example, a BP pulse (e.g., impulse bias) provided as DC power at 645 kHz may not provide supplemental plasma generation and will not disturb the plasma generated by the previous SP pulse or the corresponding afterglow.

[0036] Similarly, above a certain critical BP pulse duration t C The duration of a long BP pulse can create strong coupling, leading to undesirable changes in plasma structure. For example, a potential drawback of longer durations is that the plasma may begin to deplete, altering its structure. The critical BP pulse duration t... C The specific value can also depend on several factors and can, for example, range from approximately 25 μs to approximately 300 μs. This may affect t. C One factor contributing to the specific value is that BP alters the electron temperature T. e The rate at which BP increases T is relatively slow. e It may lead to t C The value is relatively large.

[0037] Therefore, apply a pulse with a frequency f less than the critical BP frequency. C LBP pulse frequency f L and less than the critical BP pulse duration t C LBP pulse duration tL The LBP pulse is adjusted to remain within the optimal region 11 and avoid strong coupling. For example, in some cases, the LBP pulse frequency f is approximately 400 kHz. L It is the desired frequency because it correlates well with the plasma generation or electron temperature T. e Increase separation. However, although not necessary, HBP pulses can be appropriately combined with LBP pulses while still maintaining weak or no coupling, as described below.

[0038] Figure 2 A schematic timing diagram of another example plasma processing method according to an embodiment of the present invention, a corresponding qualitative curve of ion density and potential at the substrate, and a schematic diagram of the possible effects of an HBP pulse at the substrate are shown. For example, Figure 2 The illustrative timing diagram may be a specific implementation of other illustrative timing diagrams described herein, such as, for example... Figure 1 A schematic timing diagram. Elements with similar markings can be described as previously.

[0039] refer to Figure 2 The schematic timing diagram 200 illustrates the application of SP and BP in the plasma processing system. During a repeatable pulse period 209, a pulse with an SP pulse frequency f is supplied to the plasma processing system. S and SP pulse duration t S SP pulse 212 and having LBP pulse frequency f L and LBP pulse duration t L The LBP pulse 222. Specifically, the pulse period 209 can be executed multiple times to perform the plasma processing method of a given embodiment. The pulse period 209 can have any suitable duration and is approximately 1 ms in one embodiment.

[0040] The pulse cycle 209 can be conceptually divided into multiple phases, such as the three phases shown in the figure. During phase 201, an SP pulse 212 is applied to the plasma processing system, while during phase 202, an LBP pulse 222 is applied. Phase 201 can be referred to as the SP phase or plasma generation phase. Phase 202 can be referred to as the BP phase or ion acceleration phase. Optionally, as shown in the figure, a phase 203 may also be included, during which the SP and BP are turned off. Phase 203 can be referred to as the shutdown phase or byproduct management phase.

[0041] Additionally, an HPB pulse 232 is provided during phase 201. The HPB pulse 232 has an HPB pulse frequency f. H HPB pulse duration t H As shown in the figure, in one embodiment, the HBP pulse duration tH With SP pulse duration t S Overlap. Alternatively, the HBP pulse duration t H It can be different from the SP pulse duration t S Alternatively or concurrently, the HBP pulse 232 may be applied during other stages as described below. For example, the HBP pulse 232 may also be applied during stage 202. The HPB pulse frequency f H Greater than the LBP pulse frequency f L For example, in various embodiments, f L Less than approximately 800kHz, while f H Greater than 800kHz. In some embodiments, f H In the HF range, and in one embodiment approximately 13.56 MHz.

[0042] The pulse may affect the ion density n at the substrate. i and root mean square potential V rms Yes, it has an impact. For example, as shown in qualitative curve 205, the ion density n i The ion density n increases during SP pulse 212 of phase 201. Due to the separation of LBP pulse 222 from the generated plasma, the ion density n... i The voltage decreases during stage 202, which may correspond to the afterglow. In contrast, the potential V at the substrate... rms The ion density n is relatively low and constant in stage 201, but increases with the application of LBP pulse 222 in stage 202. After the afterglow, the ion density n... i The voltage continues to decrease gradually, and during stage 203 when no power is applied, the potential V... rms It dropped rapidly to near zero.

[0043] The pulse timing shown in schematic timing diagram 200 can be advantageously used for a variety of plasma processing methods (e.g., for logic fabrication), such as thin etching, contour 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.

[0044] HBP pulses can be desirable for altering the rate of free radical generation (e.g., Cl) and / or influencing the etching profile. HPB pulses can also be advantageously used (e.g., during SP application in a reverse-phase process) to manage the cleanliness of a given plasma process. For example, HPB pulses can be used to control the passivation of horizontal surfaces. Referring now to schematic diagram 206, mask 55 can delineate etchable regions of 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. In some embodiments, the passivation layer 57 is an oxide. Oxides can be beneficial for sidewall protection, but when formed on horizontal surfaces, they can reduce the etching rate and pose a risk of etching stoppage. As shown in schematic diagram 206, HBP pulse 232 during stage 201 can reduce or prevent the formation of passivation layer 57 on the horizontal surface of substrate 256, which can advantageously help manage the etching front.

[0045] HBP pulse 232 is off in stage 202, while LBP pulse 222 is on. Different BP frequencies may be beneficial at different stages of a given plasma process. For example, in some cases, providing a purely lower frequency BP during the bias stage can favor increased separation. However, HBP pulse 232 can also extend into and through stages 202 and 203. Similarly, providing a higher frequency BP during the source stage can advantageously control surface interactions on the substrate surface (e.g., by suppressing oxide formation on horizontal surfaces such as feature bottoms). For example, applying HBP together with SP can maintain a potential (plasma potential V). PP and DC potential V DC ), while LBP (e.g., 400kHz) makes V in the afterglow PP Maximize. As discussed above, the HBP pulse can also be omitted (e.g., when potential control at the substrate is less important during the source phase).

[0046] One specific embodiment of the plasma processing method shown in the schematic timing diagram 200 can be silicon (Si) etching using a 50:50 HBr and Ar gas mixture with CF4 and O2 additives. In this specific example, an SP pulse power of approximately 500 W can be used. S Apply SP pulse 212, where t S Approximately 20 μs and f S Within the HF range (e.g., 13.56MHz, 26MHz, etc.), an HBP pulse power of approximately 100W can be used for the same duration and timing as the SP pulse 212. H Apply HBP pulse 232(t) H =20μs), where f HApproximately 13.56 MHz. This can be achieved over a longer duration (t...). L =80μs) using approximately 500W of LBP pulse power P L Apply LBP pulse 222, where f L The frequency is approximately 400 kHz. Stage 203 can be implemented as a shutdown stage to control byproducts and can have a duration of approximately 900 μs. Therefore, in this specific example, the duration of pulse period 209 can be approximately 1 ms.

[0047] Figure 3 A schematic timing diagram of yet another example plasma processing method according to an embodiment of the present invention, and corresponding qualitative curves of ion density and potential at the substrate are shown. For example, Figure 3 The illustrative timing diagram may be a specific implementation of other illustrative timing diagrams described herein, such as, for example... Figure 1 A schematic timing diagram. Elements with similar markings can be described as previously.

[0048] refer to Figure 3 A schematic timing diagram 300 illustrates the application of SP and BP in a plasma processing system. SP pulses 312, HBP pulses 332, and LBP pulses 322 are supplied to the plasma processing system during repeatable pulse cycles 309. Unlike... Figure 2 The schematic timing diagram 200 shows the HBP pulse duration t in the schematic timing diagram 300. H This is equal to the duration of the pulse period 309. Such application of the HBP may be low-power and is related to the maintenance of plasma ignition. For example, in situations where ignition problems may exist (e.g., low pressure, long shutdown phases, etc.), a low-power HBP may be desired to maintain a small amount of plasma to facilitate reliable re-ignition of the plasma during the subsequent source phase.

[0049] Qualitative curve 305 shows the effect of the extended duration of the HBP pulse 332 on the ion density n at the substrate. i and electric potential V rms The influence of n. As shown in the figure, n i and V rms The behavior in phases 301 and 302 is similar to that in Figure 2 The corresponding behaviors in stages 201 and 202. However, in stage 303, HBP pulse 332 will n i and V rms It remains at a relatively constant non-zero value. (With n) i and V rms They can all be ignored. Figure 2Compared to stage 203, in stage 303 corresponding to low-density plasma, HBP pulse 332 can reduce the ion density n i Maintaining the desired level. This "tickle" plasma can advantageously facilitate easier ignition immediately after stage 303.

[0050] Additionally, it should be noted that in this case, maintaining the HBP pulse 332 throughout stage 302 can increase the ion flux in that stage. However, in some cases, HBP can also be turned off during stage 302. The feasibility of maintaining the HBP pulse during stage 302 may depend on the impact of by-product redeposition in a given process.

[0051] Figure 4 Schematic timing diagrams of various plasma processing methods according to embodiments of the present invention are shown. For example, Figure 4 The illustrative timing diagram may be a specific implementation of other illustrative timing diagrams described herein, such as, for example... Figure 1 A schematic timing diagram. Elements with similar markings can be described as previously.

[0052] refer to Figure 4 Several schematic timing diagrams illustrate non-exhaustive sampling of 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 an LBP pulse 422, and is conceptually divided into three phases (phase 1, phase 2, and phase 3). These diagrams differ from each other in that they may also include various HBP pulses and additional SP pulses with varying durations and timings.

[0053] Figure (a) depicts something similar to Figure 3 The difference lies in the application of an HBP pulse 433 for a duration that extends through stages 1 and 2 and partially through stage 3. Figures (b) and (c) depict two alternative cases: an HBP pulse 434 that extends only partially through stage 2; and an HBP pulse 435 that is applied for a duration that terminates simultaneously with the LBP pulse 422. In these and other cases, the HBP pulse may be primarily used to sustain ignition rather than to energize (i.e., accelerate) the ions.

[0054] In the same manner, Figure (d) depicts a similar... Figure 2In this case, HBP pulse 432 is applied simultaneously with SP pulse 412, and another HBP pulse 436 is applied simultaneously with LBP pulse 422. Therefore, the timing situation depicted in Figure (d) is similar to that in Figure (c), except that there is an HBP off interval between SP pulse 412 and LBP pulse 422. In Figure (d), HBP pulse 432 and the other 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 can be supplied during LBP pulse 422, as shown in Figure (e).

[0055] Figure (f) depicts a situation similar to Figure (a), but with a low-power SP pulse 416. For example, the SP pulse 412 can have a first SP pulse power P of approximately 500W. S1 The low-power SP pulse 416 can have a second SP pulse power of approximately 100W. S2 P can be used. S1 With P S2 Any relationship between them, and that relationship can depend on the specific requirements of a given plasma processing method. For example, P S2 Relative to P S1 The lower power can be used to provide a small amount of additional plasma. Furthermore, as shown in Figures (g), (h), and (i), continuous low-power SP pulses 417 can also be applied throughout phases 2 and 3. When the SP is activated in phase 3, it may reduce the ion density and increase the ion flux, which is desirable in some cases.

[0056] It should be noted that, in reality, there may be a delay between SP pulse 412 and low-power SP pulse 416, although there may also be no delay as shown in the figure. For example, the delay may be approximately 5 μs or any other value. Factors such as the frequency and duty cycle of the applied SP may affect the delay value between SP pulse 412 and subsequent SP pulses (i.e., low-power SP pulse 416, followed by consecutive low-power SP pulses 417).

[0057] Although Figure 4 Various timing scenarios have been described herein, but any suitable combination of these and other embodiments described herein, including at least one SP pulse and at least one LBP pulse, can be made to meet the specific needs of a particular application of the invention. Although shown as such, it is not required that the HBP pulse start simultaneously with the SP or LBP pulse. In other words, the start of any HBP pulse shown can be time-shifted relative to the SP or LBP pulse, in a manner similar to... Figure 4 The timing of the HBP pulse ending is shown.

[0058] Figure 5 Schematic timing diagrams and corresponding qualitative curves of electron density and ion flux are shown for several plasma processing methods according to embodiments of the present invention. For example, Figure 5 The illustrative timing diagram may be a specific implementation of other illustrative timing diagrams described herein, such as, for example... Figure 1 A schematic timing diagram. Elements with similar markings can be described as previously.

[0059] refer to Figure 5 Schematic timing diagram 501 depicts the application of SP pulse 512 without the application of BP. Electron density n e The qualitative curves corresponding to n and ion flux show that n e Ion flux is higher during SP pulse 512 and then decreases after SP termination. Ion flux decreases rapidly, while n... e It decreases at a gradually increasing, essentially constant rate. An LBP pulse duration t is introduced after SP pulse 512. L The LBP pulse 522 can change n e The decreasing rate is illustrated in schematic timing diagram 502. Specifically, it has a sufficiently long t... L The LBP pulse 522 can perturb the plasma, causing it to deplete more quickly. For example, ion flux can reflect the background plasma density. However, it may be desirable to generate more ion flux (e.g., dose) before applying another SP pulse.

[0060] For example, a sufficiently short LBP pulse can affect ion flux without strongly perturbing the background plasma. In other words, the impulse bias extracts flux without perturbing the afterglow. This can be seen in schematic timing plot 503, which shows that a sufficiently short LBP pulse (i.e., LBP spike 526) generates a corresponding spike in the ion flux, while n e Unaffected. As shown in the figure, LBP spike 526 has a sufficiently short LBP spike duration t. k In order to increase ion flux while reducing background plasma (i.e., n) e It has minimal or no impact. In various embodiments, t K Less than 20 μs and in some embodiments less than 10 μs. In one embodiment, t K Approximately 10 μs. In another embodiment, t K Approximately 1 μs.

[0061] LBP spike 526 can be similar to the LBP pulse described above, but with a shorter duration (i.e., t). KFor example, LBP spike 526 can be a BP applied at a frequency less than about 645 kHz (e.g., 400 kHz). Additionally, and similarly to the previously described LBP pulse, LBP spike 526 can also be CW DC power. For example, in one embodiment, LBP spike 526 is the application of CW DC power, wherein the LBP spike duration t K Approximately 10 μs. In other embodiments, the CW DC power can be applied for a longer or shorter duration.

[0062] As previously mentioned, longer LBP pulses can lead to parasitic plasma generation and / or alterations in plasma structure. However, for BP “pulse trains,” parasitic plasma generation may gradually increase. Therefore, as illustrated in schematic timing diagram 504, multiple appropriately spaced LBP spikes 526 can advantageously generate a relatively constant ion flux without exhausting the afterglow. For example, a dose sequence in terms of energy (e.g., gradually increasing with decreasing background density) can advantageously result in more monoenergetic beams.

[0063] The spacing t between adjacent LBP spikes 526 D It can depend on various factors, such as the frequency of the applied BP and t. K The length of t, etc. However, t can be... D The choice is made to avoid perturbations of the background plasma (e.g., short enough without raising the electron temperature T). e For example, in various embodiments, t D Greater than t K In some embodiments, t D Between approximately 20 μs and approximately 100 μs. In other embodiments, t D Between approximately 10 μs and approximately 50 μs.

[0064] In some cases, surface charging can be problematic when LBP pulses and / or LBP spikes are applied (e.g., for dielectric substrates, etc.). The magnitude of the charging effect may depend on the material contained in a given substrate, and in some cases, the charge may dissipate sufficiently between LBP spikes. However, in other cases, it may be desirable to counteract undesirable charging effects by using bipolar DC power against the LBP spikes 526. For example, every other LBP spike can be positive, or other modes can be used, such as ----+++, --+, etc. Additionally, the duration of a positive LBP spike may differ from the duration of a negative LBP spike. Furthermore, although three LBP spikes 526 are shown, this is not intended to impose a limitation on the number of LBP spikes 526. The number of LBP spikes 526 per cycle can depend on the pulse cycle time, dose requirements, and other considerations specific to a given application.

[0065] In addition to multiple LBP spikes 526, an HBP pulse 532 can be incorporated to promote chemical control during SP activation, as shown in schematic timing diagram 505. As illustrated, the ion flux during SP pulse 512 is likely to be minimally affected by the potential introduced by HBP pulse 532. This combination allows the advantages of the previously described HBP power to be combined with the advantages of LBP spikes. It should be noted that LBP spikes can be incorporated into any of the timing configurations described herein. In other words, the scope of this invention is intended to include LBP spikes as an alternative implementation of any LBP pulse described herein.

[0066] Figure 6 A schematic block diagram of an example plasma processing system according to an embodiment of the present invention is shown. Figure 6 The plasma processing system and plasma processing apparatus can be used to implement any illustrative timing diagram to perform the plasma processing methods described in the embodiments herein, for example, such as Figures 1 to 5 A schematic timing diagram. Furthermore, Figure 6 The plasma processing system and plasma processing apparatus can be used to perform any of the methods described herein, for example, such as Figure 7 and Figure 8 Plasma processing methods.

[0067] refer to Figure 6 The plasma processing system 600 includes a plasma processing apparatus 50, which includes 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 a quartz window 52 of the plasma processing apparatus 50, the SP coupling element 60 can also be implemented as a conductive plate inside the processing chamber 54 and 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 SP to the processing chamber 54 such that plasma 58 is generated inside the processing chamber 54. Plasma 58 can be any type of plasma, such as inductively coupled plasma (ICP), capacitively coupled plasma (CCP), surface wave plasma (SWP), etc.

[0068] A substrate holder 70 (e.g., an electrostatic chuck) is disposed within the processing chamber 54. The substrate holder 70 is configured to support the substrate 65. The substrate holder 70 is further configured to couple a BP to the processing chamber 54. As described herein, the coupled BP may include both an HBP and an LBP.

[0069] SP can be supplied to the machining chamber 54 using an SP control path, which 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. Additionally, the SP supply node 62 and the SP controller 64 can be combined. An optional SP matching level 65 may also be included between the SP coupling element 60 and the SP supply node 62.

[0070] Similarly, HBP and LBP can be supplied to the processing chamber 54 using separate or combined BP control paths, which include HBP supply nodes 72 and 82 coupled to the substrate holder 70 and the HBP controller 74 and LBP controller 84, respectively, as shown in the figure. As with SP, one or both of HBP supply node 72 and LBP supply node 82 can also be coupled to or include a corresponding waveform generator. Again, as previously mentioned, optional HBP matching stages 75 and / or optional LBP matching stages 85 can be included between the substrate holder 70 and the corresponding supply nodes. In some cases (e.g., for bipolar DC LBP pulses / spikes), LBP supply node 82 can be divided into positive LBP power supply and negative LBP power supply.

[0071] The controllers (i.e., SP controller 64, HBP controller 74, and LBP controller 84) are configured to control the timing of the pulses during the cyclic plasma process. As previously stated, the relative timing is fully customizable. Each of the SP pulse, HBP pulse, and LBP pulse can be in phase, partially overlap, or out of phase with respect to each other.

[0072] Figure 7 An example plasma processing method according to an embodiment of the present invention is illustrated. It can be performed using the schematic timing diagrams and embodiment plasma processing systems and apparatus as described herein. Figure 7 Plasma processing methods. For example, Figure 7 Plasma processing methods can be combined with Figures 1 to 6 Any combination of the embodiments. The method steps described below can be performed in any suitable order as will be apparent to those skilled in the art.

[0073] refer to Figure 7The plasma processing method 700 includes step 701 of providing an SP pulse to an SP coupling element during the SP pulse duration to generate plasma in a processing chamber. Step 702 includes providing an HBP pulse to a substrate holder disposed in the processing chamber during an HBP pulse duration overlapping 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 during an LBP pulse duration not overlapping with the SP pulse duration. The LBP pulse has an LBP pulse frequency less than approximately 800 kHz.

[0074] Figure 8 Another example plasma processing method according to an embodiment of the present invention is illustrated. It can be performed using the schematic timing diagrams and embodiment plasma processing systems and apparatus as described herein. Figure 8 Plasma processing methods. For example, Figure 8 Plasma processing methods can be combined with Figures 1 to 6 Any combination of the embodiments. Further, Figure 8 The plasma processing methods described herein are not intended to be mutually exclusive with other plasma processing methods described herein. For example, Figure 8 Plasma processing methods can be combined with Figure 8 The plasma processing methods are combined. The method steps described below can be performed in any suitable order as will be apparent to those skilled in the art.

[0075] refer to Figure 8 Step 801 of the plasma processing method 800 includes providing an SP pulse to an SP coupling element during the SP pulse duration to generate plasma in a processing chamber. Step 802 includes providing a plurality of BP pulses to a substrate holder disposed in the processing chamber during 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.

[0076] Exemplary embodiments of the invention are summarized herein. Other embodiments may also be understood from the entire specification and the claims set forth herein.

[0077] Example 1. A plasma processing method comprising: providing a first SP pulse to an SP coupling element during a first source power (SP) pulse duration to generate plasma in a processing chamber; providing an HBP pulse to a substrate holder disposed in the processing chamber during a high-frequency bias power (HBP) pulse duration overlapping with the first SP pulse duration, the HBP pulse including an HBP pulse frequency greater than 800 kHz; and providing a first LBP pulse to the substrate holder during a first low-frequency bias power (LBP) pulse duration not overlapping with the first SP pulse duration, the first LBP pulse including an LBP pulse frequency less than about 800 kHz.

[0078] Example 2. The plasma processing method as described in Example 1, wherein the duration of the HBP pulse completely overlaps with both the duration of the first SP pulse and the duration of the first LBP pulse.

[0079] Example 3. The plasma processing method as described in Example 1, wherein the duration of the HBP pulse completely overlaps with and is equal to the duration of the first SP pulse.

[0080] Example 4. The plasma processing method as described in any one of Examples 1 to 3, further comprising: providing a second SP pulse to the SP coupling element after the duration of the first SP pulse, during a second SP pulse duration overlapping with the duration of the first LBP pulse; wherein the first SP pulse includes a first SP pulse power; and wherein the second SP pulse includes a second SP pulse power less than the first SP pulse power.

[0081] Example 5. A plasma processing method as described in any one of Examples 1 to 4, wherein the duration of the first SP pulse is approximately 20 μs, and wherein the duration of the first LBP pulse is approximately 80 μs.

[0082] Example 6. The plasma processing method as described in any one of Examples 1 to 5 further includes: providing a second SP pulse to the SP coupling element during a second SP pulse duration after the first LBP pulse duration; and providing a second LBP pulse to the substrate holder during a second LBP pulse duration that does not overlap with the second SP pulse duration.

[0083] Example 7. The plasma processing method as described in Example 6 further includes: after the duration of the first LBP pulse, during a delay duration, neither SP is provided to the SP coupling electrode nor LBP is provided to the substrate holder; and wherein the second SP pulse is provided after the delay duration.

[0084] Example 8. The plasma processing method as described in Example 7, wherein: 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 duration; and the HBP pulse includes an HBP power less than the LBP pulse power of the first LBP pulse.

[0085] Example 9. A plasma processing method comprising: providing a first SP pulse to an SP coupling element during a first source power (SP) pulse duration to generate plasma in a processing chamber; and providing a plurality of BP pulses to a substrate holder disposed in the processing chamber during a first bias power (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 of less than about 800 kHz and a BP pulse duration of less than about 10 μs.

[0086] Example 10. The plasma processing method as described in Example 9 further includes: providing a high-frequency bias power (HBP) pulse to the substrate holder during a second BP pulse duration that overlaps with the duration of the SP pulse, the HBP pulse comprising a frequency greater than 800 kHz.

[0087] Example 11. The plasma processing method as described in Example 10, wherein the duration of the second BP pulse completely overlaps with and is equal to the duration of the SP pulse.

[0088] Example 12. A plasma processing method as described in any one of Examples 9 to 11, further comprising: providing a second SP pulse to the SP coupling element during a second SP pulse duration after the first BP pulse duration; and providing a second plurality of BP pulses to the substrate holder during a second BP pulse duration that does not overlap with the second SP pulse duration.

[0089] Example 13. A plasma processing method as described in any one of Examples 9 to 12, wherein each of the plurality of BP pulses is a single direct current (DC) pulse.

[0090] Example 14. The plasma processing method as described in Example 13, wherein a portion of the plurality of BP pulses is a positive DC pulse, and wherein the remainder of the plurality of BP pulses is a negative DC pulse.

[0091] Example 15. A plasma processing method as described in any one of Examples 9 to 14, wherein each of the plurality of BP pulses comprises a BP pulse duration of less than about 1 μs.

[0092] 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 provide a first direct current (DC) bias power to the substrate holder, the first DC bias power including a first BP frequency of less than about 800 kHz; and a second BP supply node coupled to the substrate holder and configured to provide a second DC bias power to the substrate holder, the second DC bias power including a second BP frequency of greater than 800 kHz.

[0093] Example 17. A plasma processing apparatus as described in Example 16, wherein the first BP frequency is approximately 400 kHz.

[0094] Example 18. A plasma processing apparatus as described in one of Examples 16 and 17, wherein the second BP frequency is approximately 13 MHz.

[0095] Example 19. A plasma processing apparatus as described in 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 inductively coupled plasma in the processing chamber; and the RF power includes an RF power frequency equal to about 27 MHz.

[0096] Example 20. A plasma processing apparatus as described 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 bias power and the second DC bias power to the substrate holder.

[0097] Although the invention has been described with reference to illustrative embodiments, this description is not intended to be limiting. Various modifications and combinations thereof will be apparent to those skilled in the art from the description, illustrative embodiments, and other embodiments of the invention. Therefore, it is intended that the appended claims cover any such modifications or embodiments.

Claims

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 a 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 overlapping at least a portion of the first SP pulse duration, the HBP pulse comprising an HBP pulse frequency greater than 800 kHz; and providing a first low frequency bias power (LBP) pulse to the substrate holder for a first LBP pulse duration not overlapping the first SP pulse duration, the first LBP pulse comprising an LBP pulse frequency less than 800 kHz. The HBP pulse duration fully overlaps both the first SP pulse duration and the first LBP pulse duration.

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

3. The plasma processing method of claim 1, wherein, 4. The plasma processing method of claim 1, further comprising: providing a second SP pulse to the SP coupling element for a second SP pulse duration overlapping at least a portion of the first LBP pulse duration after the first SP pulse duration; wherein the first SP pulse comprises a first SP pulse power; and wherein the second SP pulse comprises a second SP pulse power less than the first SP pulse power. The first SP pulse duration is 20 ps, and wherein the first LBP pulse duration is 80 ps.

5. The method of plasma processing of claim 1 wherein, 6. 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 a plasma in a processing chamber; providing a plurality of bias power (BP) pulses to a substrate holder disposed in the processing chamber during a first BP pulse duration not overlapping 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 ps.

7. The plasma processing method of claim 6, further comprising: providing a high frequency bias power (HBP) pulse to the substrate holder for a second BP pulse duration overlapping the first SP pulse duration, the HBP pulse comprising a frequency greater than 800 kHz. The second BP pulse duration fully overlaps and is equal to the first SP pulse duration. Each of the plurality of BP pulses is a single direct current (DC) pulse.

8. The method of plasma processing of claim 7, wherein, A portion of the plurality of BP pulses are positive DC pulses, and wherein a remaining portion of the plurality of BP pulses are negative DC pulses.

9. The method of plasma processing as claimed in claim 6, wherein, Each of the plurality of BP pulses comprises a BP pulse duration less than 1 ps.

10. The method of plasma processing of claim 9, wherein, 12. A plasma processing apparatus, comprising:

11. The method of plasma processing as recited in claim 6, wherein, a processing chamber; a source power (SP) coupling element configured to generate a plasma in the processing chamber; a substrate holder disposed in the processing chamber; and a bias power (BP) source configured to provide a plurality of BP pulses to the substrate holder, each of the plurality of BP pulses comprising a BP pulse frequency less than 800 kHz. an SP power supply node coupled to the source power SP coupling element and configured to supply radio frequency, RF, power to the source power SP coupling element for a first SP pulse duration; a substrate holder disposed in the process 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 for a first BP pulse duration that does not overlap the first SP pulse duration, the first DC bias power comprising a first BP frequency less than 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 for a second BP pulse duration that overlaps at least a portion of the first SP pulse duration, the second DC bias power comprising a second BP frequency greater than 800 kHz. The first BP frequency is 400 kHz.

13. The plasma processing apparatus of claim 12, wherein, The second BP frequency is 13 MHz.

14. The plasma processing apparatus of claim 13, wherein, 15. The plasma processing apparatus of claim 14, wherein: the source power SP coupling element is a helical resonator disposed outside the process chamber and configured to generate an inductively coupled plasma in the process chamber; and the RF power comprises an RF power frequency equal to 27 MHz.

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

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