Remote Source Pulsing Using Advanced Pulse Control

Abstract

1. A method of etching a substrate, comprising: applying a first power pulse for a first duration to a first electrode located in a first chamber to generate a first plasma from a first gas flowing into the first chamber; forming a recess in a substrate located in a second chamber, the forming comprising: supplying radicals from the first chamber into the second chamber; applying a plurality of second power pulses for a second duration to a second electrode located in the second chamber to generate a second plasma in the second chamber from a second gas flowing into the second chamber, the first chamber being pressurized at a higher pressure than the second chamber; and applying a plurality of third power pulses for a third duration to a third electrode located in the second chamber to accelerate ions of the second plasma.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. patent application Ser. No. 17 / 550,651, entitled "Remote Source Pulsing with Advanced Pulse Control," filed December 14, 2021, the disclosure of which is expressly incorporated by reference in its entirety into this specification.

[0002] The present invention relates generally to methods for processing substrates and, in a specific embodiment, to remote source pulsing using advanced pulse control. [Background technology]

[0003] Generally, semiconductor devices, such as integrated circuits (ICs), are fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconducting materials on a substrate to form a network of monolithically integrated electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias). Many of the processing steps used to form the constituent structures of semiconductor devices are performed using plasma processing.

[0004] The semiconductor industry is repeatedly shrinking the minimum feature size in semiconductor devices down to a few nanometers to increase the packing density of components, enabling the fabrication of three-dimensional (3D) devices such as fin field effect transistors (FinFETs), gate-all-around field effect transistors (GAAFETs), and 3D NAND memory. In response, the semiconductor industry is increasingly demanding plasma processing technologies to provide processes that pattern features with accuracy, precision, and profile control, often at atomic-scale dimensions. Meeting this challenge with the uniformity and repeatability required for high-volume IC production requires further innovation in plasma processing technologies. Summary of the Invention [Means for solving the problem]

[0005] According to an embodiment of the invention, a method of etching a substrate includes: generating a first plasma from a first gas flowing into the first chamber by applying a first power pulse for a first duration to a first electrode located in a first chamber; forming a recess in a substrate located in a second chamber, where forming includes supplying radicals from the first chamber into the second chamber; applying a plurality of second power pulses for a second duration to a second electrode located in the second chamber to generate a second plasma in the second chamber from a second gas flowing into the second chamber, where the first chamber is pressurized at a higher pressure than the second chamber; and applying a plurality of third power pulses for a third duration to a third electrode located in the second chamber to accelerate ions of the second plasma.

[0006] According to one embodiment of the present invention, a method for processing a substrate in a plasma processing chamber includes: flowing a first gas into a remote source (RS) chamber maintained at a first pressure, the RS chamber connected to the plasma processing chamber; flowing a second gas into the plasma processing chamber maintained at a second pressure, the second pressure being lower than the first pressure; and performing a cyclic process including a plurality of cycles, each cycle of the plurality of cycles including generating a first plasma of a first gas to generate radicals, supplying the radicals to the plasma processing chamber, and performing an etching process in the plasma processing chamber in the presence of the radicals to form a recess in the substrate.

[0007] According to one embodiment of the present invention, a plasma processing system includes a remote source (RS) chamber including a gas inlet, a first electrode coupled to a radio frequency (RF) power source, the first electrode configured to generate a first plasma including radicals in the RS chamber, and an outlet for the radicals; a plenum attached to the outlet of the RS chamber, the plenum made of a first thermal conductor, and a wall of the plenum including an opening for gas flow; and a plasma process chamber connected to the RS chamber through the plenum, the plasma process chamber including a substrate holder disposed below the plenum, a gas outlet below the substrate holder, a second electrode coupled to a process power source, the second electrode configured to generate a second plasma, a third electrode coupled to a first bias power source, the third electrode configured to accelerate ions of the second plasma, and process chamber walls including a second thermal conductor, the process chamber walls of the process chamber being thermally coupled to the walls of the plenum.

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

[0009] [Figure 1A] 1 illustrates a schematic timing diagram of three process parameters (i.e., remote source power, process source power, and bias source power) of an exemplary remote source mediated plasma etch process, in accordance with various embodiments. [Figure 1B] 1B shows corresponding quantitative graphs of radical density and ion density during the exemplary plasma treatment of FIG. 1A. [Figure 2A]3A and 3B show schematic timing diagrams of remote source power and gas flow rates for a remote source chamber during plasma processing using a remote source according to various embodiments, with FIG. 3A showing an embodiment using one gas composition and FIG. 3B showing an embodiment using two gas compositions. [Figure 2B] 3A and 3B show schematic timing diagrams of remote source power and gas flow rates for a remote source chamber during plasma processing using a remote source according to various embodiments, with FIG. 3A showing an embodiment using one gas composition and FIG. 3B showing an embodiment using two gas compositions. [Figure 3A] 3A and 3B show schematic timing diagrams of remote source power during plasma processing using a remote source according to alternative embodiments, where FIG. 3A shows an embodiment using a constant remote source power and FIG. 3B shows another embodiment using two levels of remote source power. [Figure 3B] 3A and 3B show schematic timing diagrams of remote source power during plasma processing using a remote source according to alternative embodiments, where FIG. 3A shows an embodiment using a constant remote source power and FIG. 3B shows another embodiment using two levels of remote source power. [Figure 4A] 4A and 4B show schematic timing diagrams of process source power and bias source power during plasma processing using a remote source according to various embodiments, with FIG. 4A showing an embodiment using overlapping power pulse trains and FIG. 4B showing another embodiment using in-phase power pulse trains. [Figure 4B] 4A and 4B show schematic timing diagrams of process source power and bias source power during plasma processing using a remote source according to various embodiments, with FIG. 4A showing an embodiment using overlapping power pulse trains and FIG. 4B showing another embodiment using in-phase power pulse trains. [Figure 5A] 5A-5B show cross-sectional views of an exemplary substrate during plasma processing according to various embodiments, with FIG. 5A showing an embodiment with saturation of radicals on the substrate and FIG. 5B showing an alternative embodiment with insufficient radical coverage. [Figure 5B]5A-5B show cross-sectional views of an exemplary substrate during plasma processing according to various embodiments, with FIG. 5A showing an embodiment with saturation of radicals on the substrate and FIG. 5B showing an alternative embodiment with insufficient radical coverage. [Figure 6A] 6A shows a process flow chart for a plasma processing method using a remote source according to various embodiments, where FIG. 6A shows the process flow of an embodiment, FIG. 6B shows another embodiment including a cyclic process, FIG. 6C shows an exemplary etch process for the cyclic process of FIG. 6B, and FIG. 6D shows the process flow of an alternative embodiment. [Figure 6B] 6A shows a process flow chart for a plasma processing method using a remote source according to various embodiments, where FIG. 6A shows the process flow of an embodiment, FIG. 6B shows another embodiment including a cyclic process, FIG. 6C shows an exemplary etch process for the cyclic process of FIG. 6B, and FIG. 6D shows the process flow of an alternative embodiment. [Figure 6C] 6A shows a process flow chart for a plasma processing method using a remote source according to various embodiments, where FIG. 6A shows the process flow of an embodiment, FIG. 6B shows another embodiment including a cyclic process, FIG. 6C shows an exemplary etch process for the cyclic process of FIG. 6B, and FIG. 6D shows the process flow of an alternative embodiment. [Figure 6D] 6A shows a process flow chart for a plasma processing method using a remote source according to various embodiments, where FIG. 6A shows the process flow of an embodiment, FIG. 6B shows another embodiment including a cyclic process, FIG. 6C shows an exemplary etch process for the cyclic process of FIG. 6B, and FIG. 6D shows the process flow of an alternative embodiment. [Figure 7] 1 illustrates a plasma system using a remote radical source for performing a semiconductor manufacturing process, according to various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present application relates to a system and method for plasma processing during the manufacturing of semiconductor devices, and more particularly, to a remote source (RS) mediated plasma etch process using advanced pulse control, where the RS is used to deliver radicals to a plasma processing chamber. In the manufacturing of 3D semiconductor devices such as FinFETs, plasma etch processes can encounter various complex challenges, such as line edge roughness, critical dimension (CD) loss, and aspect ratio dependent etching (ARDE), among others. Due to the complexity of plasma etch processes, optimizing process parameters for some metrics may degrade other metrics. For example, low pressure and low duty cycle conditions may be desired for sufficient ion verticality for anisotropic etching and for less by-product redeposition. However, such conditions can often cause radical depletion during the process, leading to loss of profile control and etch rate. An embodiment of the present application discloses a method for plasma etch processing using a combination of advanced pulse control and a RS to provide radicals that enable conformal coverage of radicals.

[0011] The methods described in the present disclosure allow for sufficient radicals to be delivered from a remote source (RS) to a plasma processing chamber, which can advantageously improve ion verticality and therefore anisotropy of the plasma etch process. The anisotropy can be improved because conformal surface coverage of neutral species (e.g., radicals) on the substrate can passivate the sidewalls of features. Thus, critical dimension (CD) loss during plasma etch processing can be reduced according to various embodiments. In addition, the vertical etch rate can also be maximized by minimizing the loss of ion energy at the sidewalls. Furthermore, the methods herein can adjust the ratio of neutral flux to ion flux without substantially changing the conditions (e.g., pressure or duty cycle) of the plasma processing chamber. For example, various embodiments advantageously increase the flux of neutral species without requiring pressure throttling of the plasma processing chamber. To further improve process efficiency with the methods of the embodiments, the RS and the plasma processing chamber may be independently powered using different sets of power pulse trains. As a result, the methods herein enable low pressure plasma etch processes for etching recessed features having high aspect ratios (HAR) useful in various 3D semiconductor devices. In addition, the methods of the embodiments may also be beneficial for mitigating aspect ratio dependent etching (ARDE).

[0012] First, in the following, FIG. 1A shows an exemplary RS-mediated plasma etching process with an exemplary time chart according to various embodiments. The corresponding radical density and ion density are described with reference to FIG. 1B. In FIG. 2A-2B, gas flow control for RS is described. Time charts for different power pulse trains for powering and controlling plasma are shown in FIG. 3A-3B for RS and in FIG. 4A-4B for process source (PS) and bias source (BS). The effect of RS-mediated radical saturation on ion verticality is described with reference to FIG. 5A-5B. Then, an exemplary process flow diagram is shown in FIG. 6A-6D. FIG. 7 provides an exemplary plasma system with RS for performing a semiconductor manufacturing process according to various embodiments. As described in more detail with reference to FIG. 7, a plasma system for RS-mediated plasma etching process may include three sections: an RS chamber, a plenum including a radical ballast region, and a plasma processing chamber. All figures are drawn for illustrative purposes only and are not to scale.

[0013] A remote source (RS) mediated plasma etch process according to various embodiments includes a passivation phase and an etching phase. The passivation phase may include generating radicals in the RS chamber and transporting the radicals from the RS chamber to the plasma processing chamber through a radical ballast region. In various embodiments, a first plasma may be generated in the RS chamber to generate radicals during the passivation phase. The first plasma may be generated by applying an RS pulse to a coupling element (e.g., a coil of a helical resonator) of the RS chamber to generate the first plasma. The etching phase may then include generating a second plasma in the plasma processing chamber (i.e., a generation phase), accelerating ions of the second plasma (i.e., an ion energy phase), and exposing a substrate to the accelerated ions of the second plasma in the presence of radicals provided from the RS chamber to form features (e.g., recesses) in the substrate. The generation phase may include applying one or more PS pulses to a coupling element of the plasma processing chamber. The ion energy phase may include applying one or more BS pulses to a substrate holder of the plasma processing chamber to direct ions toward a substrate supported by the substrate holder. Additionally, during the etching phase, a third phase (i.e., a by-product management phase) may be utilized, during which the PS power and / or BS power are off or reduced to enable control of by-products within the plasma processing chamber.

[0014] In various embodiments, the above steps of the RS-mediated plasma etch process may be performed, for example, by using a set of power pulse trains, as described in further detail below.

[0015] FIG. 1A illustrates a schematic timing diagram for three process parameters of an exemplary plasma process, in accordance with various embodiments.

[0016] FIG. 1B shows corresponding quantitative graphs of radical density and ion density during the exemplary plasma treatment of FIG. 1A.

[0017] In FIG. 1A, a timing diagram shows the RS power in the RS chamber, and the process source (PS) power and bias source (BS) power in the plasma processing chamber. c represents one cycle of plasma treatment including a passivation phase (t1) and an etching phase (t2). During the passivation phase (t1), as shown in FIG. 1A, power can be supplied to the RS to generate radicals by applying an RS power pulse 10 to the RS electrode of the RS chamber for a pulse duration d1 while flowing a first gas through the RS chamber. In various embodiments, a first plasma having a high radical density can be generated by applying the RS power pulse 10. In certain embodiments, the RS power pulse 10 may include a train of power pulses. The pulse duration d1 may be set approximately on the scale of the residence time of the formed radicals. The residence time of the formed radicals depends on various parameters such as gas flow rate, pressure, volume of the RS chamber, and the sticking coefficient of the radical species to the wall of the RS chamber. In various embodiments, the pulse duration d1 may be 1 ms to 5 seconds, and in other embodiments, 0.1 seconds to 2 seconds.

[0018] In various embodiments, the pressure of the RS chamber may be maintained between 100 mTorr and 5 Torr, and in other embodiments between 0.5 Torr and 2 Torr. The RS chamber pressure may be advantageously selected to allow for the formation of a radical-rich plasma in the RS chamber. The radicals generated in the RS chamber may be transported to the plasma processing chamber holding the substrate. Thus, the radical density 16 in the plasma processing chamber is significantly increased and maintained during the passivation phase (t1), as shown in FIG. 1B. In various embodiments, the transport of radicals may be driven or assisted by a pressure difference between the RS chamber and the plasma processing chamber. Thus, the pressure of the plasma processing chamber may be advantageously maintained lower than the pressure of the RS chamber. In various embodiments, the pressure of the plasma processing chamber may be maintained between 5 mTorr and 200 mTorr, and in certain embodiments between 10 mTorr and 100 mTorr. In other embodiments, the pressure may be 5 mTorr or less to further suppress the effects of by-product redeposition or aspect ratio dependent etching (ARDE). The ability to supply sufficient radicals to a plasma processing chamber while maintaining a relatively low chamber pressure, such as 100 mTorr or less, may be one of the advantages for RS-mediated plasma etch processes over conventional techniques that may suffer from radical depletion at such low chamber pressures.

[0019] The first gas flowed into the RS chamber may include any gas useful in plasma etching. In various embodiments, the first gas includes a fluorocarbon, such as CF4, C4F8, C4F6, CH3F, CHF3, or CH2F2, and in other embodiments, the first gas includes a halogen-containing gas, such as F2, SF6, Cl2, Br2, or HBr. In still other embodiments, the first gas may include an oxygen-containing gas, such as diatomic oxygen (O2), or a noble gas, such as helium (He), argon (Ar), or krypton (Kr). The first gas may be a gas mixture in various embodiments. Additionally, as further described in FIG. 2B below, the composition and / or gas flow rate of the first gas may be varied during the RS-mediated plasma etching process.

[0020] Then, during an etching phase (t2), power may be supplied to the process source (PS) and bias source (BS) of the plasma processing chamber to generate a second plasma (i.e., a processing plasma for etching) and accelerate ions of the second plasma, respectively, while flowing a second gas into the plasma processing chamber. In a particular embodiment, a gap (t delay ) may be present. Figure 1A shows an embodiment without a gap. The etching phase (t2) may include a generation phase, in which a second plasma is generated and powered by the PS, and an ion energy phase, in which ions of the second plasma are accelerated by the BS. These two phases of generation phase and ion energy phase may be separated (e.g. out of phase in Figure 1A), partially overlapping (e.g. in Figure 3A), or fully overlapping (e.g. in phase in Figure 3B).

[0021] The second gas flowed into the plasma processing chamber may comprise any gas useful in plasma etching. In some embodiments, the second gas may have the same composition as the first gas, but in other embodiments, may be different. For example, the first gas may comprise a reactive gas, such as a fluorocarbon, and the second gas may comprise an inert gas, such that the first gas allows for sidewall passivation and / or etching, while the second gas provides energy directed to the etch front. In certain embodiments, the second gas may comprise a noble gas, such as He, Ar, or Kr. In one embodiment, the first gas and the second gas may comprise the same gas composition to deliver reactive ions to the etch front. Such an embodiment may also be useful for generating polymerized species that may be deposited on the substrate to compensate for loss of the etch mask due to sputtering.

[0022] In one embodiment, the second gas may be Ar and may be used for processes using thick etch masks (e.g., carbon hard masks having a thickness of several microns or more) where compensation of the etch mask is not required. In another embodiment, the second gas may include 90% Ar and 10% C4F6 and a polymer may be deposited over the etch mask. In yet another embodiment, the second gas may include 10% Ar and 90% C4F6, which promotes further deposition of the polymer.

[0023] A set of power pulses may be applied to power the PS and the BS. In various embodiments, the power pulses for powering the PS may include a PS power pulse train 12 having a pulse duration d2 and a first PS power level, and the power pulses for powering the BS may include a BS power pulse train 14 having a pulse duration d3 and a first BS power level. In FIG. 1A, as an illustrative example, the PS power pulse train 12 and the BS power pulse train 14 both have the same frequency 1 / t3. In other words, one on-off cycle of the PS pulse and the BS pulse has a period t3. However, different frequencies may be used for the PS power pulse train 12 and the BS power pulse train 14. Furthermore, in the period of the etching phase (t2) in FIG. 1B, three on-off cycles (t3×3) are shown for illustrative purposes, but any number of on-off cycles may be implemented during the etching phase. In certain embodiments, the etching phase (t2) may include 100 to 1000 cycles. In other embodiments, the PS power pulse train 12, the BS power pulse train 14, or both, may have a frequency between 1 kHz and 5 kHz.

[0024] In various embodiments, the PS power pulse train 12, the BS power pulse train 14, or both, may have various duty cycles (ratio of on time to the duration of one on-off cycle) ranging from, for example, 3% to 95%. In a particular embodiment, the duty cycle of the PS power pulse train, the BS power pulse train, or both, may be from 3% to 20%.

[0025] In various embodiments, the pulse duration d2 of the PS power pulse train 12 may be between 0.1 μs and 100 μs, and in certain embodiments may be between 1 μs and 20 μs.

[0026] In various embodiments, the pulse duration d3 of the BS power pulse train 14 may be between 1 μs and 200 μs, and in particular embodiments between 5 μs and 100 μs.

[0027] In addition to the two phases (i.e., the generation phase and the ion energy phase), the etching phase (t2) may further include a by-product management phase d4 as shown in FIG. 1A. The by-product management phase may be performed to adjust the degree of redeposition of by-products on the feature. In various embodiments, during the by-product management phase, the process source (PS) power may be changed to a second PS power level that is less than the first PS level, and the bias source (BS) power may be changed to a second BS power level that is less than the first BS level. In certain embodiments, the second PS level and the second BS level may be zero (i.e., the PS power and the BS power are off), as shown in FIG. 1A. The by-product management phase d4 may have any reasonable duration. In certain embodiments, d4 may be 1 ms or longer to ensure removal of any undesired species from the substrate. In other embodiments, the by-product management phase may be skipped (i.e., d4 in FIG. 1A is equal to zero). In various embodiments, the by-product management phase may be inserted at any suitable time during the RS-mediated plasma etch process, for example, after each pulse of the BS power pulse train 14, as shown in FIG. 1A, or only after multiple pulses of the BS power pulse train 14.

[0028] In FIG. 1B, the ion density 18 in the plasma processing chamber repeatedly rises during the etching phase corresponding to the timing of the generation phase (i.e., powering the PS at a first PS power level) and decays after the generation phase (e.g., during the ion energy phase and by-products). Three repeating peaks in ion density 18 are shown, corresponding to three cycles of the generation phase. Conditions of the power pulse train, such as frequency, may be selected to provide optimal plasma conditions. For example, once the ions available for etching are depleted at the end of the first cycle (e.g., at the end of the first ion energy phase or the first by-products management phase), a second generation phase may be initiated.

[0029] Meanwhile, the radical density 16 in the plasma processing chamber may remain relatively constant with only a moderate decrease during the etching phase (t2). It should be noted that the minute decrease in radical density 16 on the illustrated time scale (e.g., less than 1 ms for several PS-BS power cycles) may be only slight, e.g., less than 5%. A relatively constant radical density 16 is possible due to the relatively long residence time of radicals (e.g., 1 ms to 1 s) compared to the short time scale (e.g., less than 1 ms) of one cycle t3. Thus, in various embodiments, hundreds of cycles may be performed after one passivation phase in radical-rich conditions. Once the radical density 16 decreases below a desired level (e.g., less than 70% of the maximum level), the etching phase may be terminated and another passivation phase may be performed to replenish the radicals in the plasma processing chamber. Thus, the remote source (RS)-mediated plasma etching process in the present disclosure may be performed cyclically by repeating the passivation phase (t1) and the etching phase (t2).

[0030] 2A and 2B show schematic timing diagrams for remote source (RS) power and gas flow rates for an RS chamber during a RS-mediated plasma etch process according to various embodiments.

[0031] In FIG. 2A, the gas flow rate of the first gas is maintained constant during both the passivation phase (t1) and the etching phase (t2). The gas flow rate may be varied between t1 and t2 in certain embodiments. Maintaining an appropriate pressure in the RS chamber is important to prevent backflow from the plasma processing chamber into the RS chamber. In the illustrated example, the first composition 22 of the first gas is held constant.

[0032] In contrast, in FIG. 2B, during the passivation phase (t1), a first composition 22 of the first gas may be flowed, and during the etching phase (t2), a second composition 24 of the first gas may be flowed at the same gas flow rate. In a particular embodiment, the first composition 22 of the first gas may include a reactive gas, such as a fluorocarbon, and the second composition 24 of the first gas may include an inert gas, such as a noble gas. Switching to an inert gas flow in the RS chamber during the etching phase (t2) may help reduce the introduction of undissociated first component reactive gas species into the plasma processing chamber. The gas composition and / or gas flow rate of the first gas may be changed at any reasonable stage during the RS-mediated plasma etching process.

[0033] Remote source (RS)-mediated plasma etch processes may be advantageously performed as an isobaric continuous process without pressure throttling of the plasma processing chamber. In contrast, conventional etching techniques that include multiple stages, such as atomic layer etching (ALE), may require pressure throttling, which complicates and slows the process. Thus, RS-mediated plasma etch processes can eliminate several steps to change conditions required in conventional etching techniques and improve process efficiency.

[0034] In addition to the embodiments described above, various combinations of power pulse trains may be used for the remote source (RS), process source (PS) and bias source (BS), as shown in Figures 3A-3B and 4A-4B. An example for powering the RS is described with reference to Figures 3A-3B, and an example for powering the PS and BS is described with reference to Figures 4A-4B.

[0035] 3A and 3B show schematic timing diagrams of RS power during plasma processing using RS according to an alternative embodiment. Any suitable pulsing pattern and conditions may be used to power the PS and BS.

[0036] In FIG. 3A, instead of using power pulses, the RS in the RS chamber is powered by applying a constant RS power 11. Thus, in such an embodiment, the passivation phase (t1) lasts for a period of one cycle of plasma processing, t c and overlaps with the etching phase (t2). By applying a constant RS power 11, radicals can be constantly generated in the RS chamber for the entire duration of the plasma treatment.

[0037] In FIG. 3B, the remote source (RS) power pulse 10 may include an RS power pulse train with two non-zero RS power levels. In the previous embodiment shown in FIG. 1A, the RS power is on only during the passivation phase (t1). In contrast, in these embodiments, when the plasma processing advances from the passivation phase (t1) to the etching phase (t2), the RS power is reduced from a first RS power level to a second RS power level lower than the first RS power level. Not completely cutting off the RS power during the etching phase may be beneficial in resuming radical generation in the next cycle (i.e., the passivation phase) and / or in ensuring re-ignition of the plasma. In certain embodiments, more complex RS power pulse train patterns may be used to power the RS.

[0038] 4A and 4B show schematic timing diagrams of process source (PS) power and bias source (BS) power during plasma processing using an RS according to various embodiments. Any suitable pulsing pattern and conditions may be used to power the RS.

[0039] In Figure 4A, the power-on periods of the PS power pulse train 12 and the BS power pulse train 14 partially overlap. In other words, the generation phase (when PS is on) and the ion energy phase (when BS is on) partially overlap. The overlapping of the two phases advantageously allows fine tuning of the plasma conditions by allowing three different power states (i.e., powered by PS only, PS and BS, and BS only).

[0040] In FIG. 4B, the power-on periods of the PS power pulse train 12 and the BS power pulse train 14 are completely overlapped, and the pulse period d2 of the PS power pulse train 12 and the pulse period d3 of the BS power pulse train 14 are identical and synchronous. Thus, the generation phase and the ion energy phase are completely overlapped (in phase), which can advantageously simplify the process and reduce the number of process parameters. Such an embodiment may lead to higher ion temperatures, which may lead to some lateral etching. The lateral etching may be beneficial to some extent, since it may help to clean the sidewalls by removing some of the redeposition of by-products. Similarly, the lateral etching may help prevent blockage problems or feature pinch-off, especially when significant passivation is used at or near the top of high aspect ratio contact (HARC) structures.

[0041] Furthermore, in other embodiments, more complex combinations of PS and RS power pulse train patterns may be used. For example, multi-frequency RF power may be used to power the BS (i.e., multiple pulse trains are used simultaneously to power the BS). In addition, instead of turning off the PS and / or BS completely, switching between two or more non-zero PS and / or BS power levels for the power pulse trains may be used. The use of multiple PS and / or BS power levels may be particularly beneficial for fine-tuning the by-product management phase.

[0042] According to the various embodiments described above, the RS-mediated plasma etching process allows maintaining a high level of radical density 16 in the plasma processing chamber. Therefore, the substrate is flooded with radicals and the surface of the substrate can be saturated with radicals. This RS-mediated radical saturation can be quite beneficial for maintaining ion verticality, as shown in Figures 5A and 5B.

[0043] 5A and 5B show cross-sectional views of an exemplary substrate 500 during plasma processing, according to various embodiments.

[0044] Substrate 500 may include a semiconductor substrate in various embodiments. In one or more embodiments, substrate 500 may be a silicon wafer or a silicon-on-insulator (SOI) wafer. In certain embodiments, substrates may include silicon germanium wafers, silicon carbide wafers, gallium arsenide wafers, gallium nitride wafers, and other compound semiconductors. In other embodiments, substrate 500 includes heterogeneous layers such as silicon germanium-on-silicon, gallium nitride-on-silicon, silicon carbon-on-silicon, as well as silicon-on-silicon layers or SOI substrates.

[0045] In FIG. 5A, an etch mask layer 510 is deposited on a substrate 500 with a pattern. An ideal etch profile with perfectly vertical sidewalls is shown resulting from a plasma etching process utilizing positively charged ions 520 to etch recesses 530 into the substrate 500. The plasma etching process can create recesses 530 with a high aspect ratio (HAR). Features with an aspect ratio (ratio of feature height to feature width) higher than 50:1 are generally considered to be high aspect ratio features, and in some cases, creating structures with higher aspect ratios such as 100:1 may be desired for advanced 3D semiconductor devices, such as contacts and other stepped structures for memory devices. In this scenario, during etching, radicals 540 saturate on the sidewalls of the recesses 530 to form a uniform surface layer that acts as a passivation layer. This can be achieved by providing sufficient radicals generated in the RS chamber to the plasma processing chamber, as described above. Since radicals 540 are electronically neutral species, saturating the sidewalls with radicals 540 prevents surface charging, thereby allowing the influx of positively charged ions 520 to maintain their verticality and reach the etch front with minimal energy loss. In other words, RS-mediated radical saturation can be used to achieve highly anisotropic etching without compromising the etch rate. Furthermore, it is well known to those skilled in the art that the structures of 3D semiconductor devices may include multiple ARs. Therefore, in order to maintain the same etching performance at different depths of features (e.g., features with different ARs), it is useful to have a uniform surface layer with conformality, as shown in FIG. 5A. Thus, the methods herein may be advantageous in mitigating the problem of aspect ratio dependent etching (ARDE).

[0046] In contrast, FIG. 5B illustrates a scenario of insufficient radical coverage on the sidewall. If the radical density in the plasma processing chamber is not high enough (e.g., radical-depleted, ion-rich situation), the sidewall of the recess 530 may not be saturated with radicals 540, which may cause some parts of the sidewall to be negatively charged. Thus, the impact of positively charged ions 520 on the sidewall may lead to lateral etching and may compromise ion verticality. This effect may result in non-uniform etching rates in the recess 530, especially on the sidewall, which may result in deformation of the feature as shown. This problem of radical depletion is one of the challenges in conventional plasma etching techniques, especially when they operate at medium to low pressures (e.g., below 100 mTorr). However, the method of the present disclosure can advantageously achieve the radical-rich, ion-depleted situation as illustrated in FIG. 5A by using RS-mediated plasma etching process.

[0047] 6A-6D show process flow diagrams of plasma processing methods using a remote source according to various embodiments. The process flow can follow the diagrams described above (e.g., FIGS. 1A and 1B), and thus will not be described again.

[0048] In Figure 6A, the process flow 60 begins with generating a first plasma from a first gas flowing into a first chamber (i.e., a remote source chamber) by applying a first power pulse for a first duration to a first electrode located in the first chamber (i.e., a remote source chamber) (block 610). The first duration corresponds to a passivation phase (e.g., t1 in Figure 1A). The next step is to form a recess in a substrate located in a second chamber (i.e., a plasma processing chamber) (block 620). Forming the recess may include supplying radicals from the first chamber into the second chamber (block 622); applying a plurality of second power pulses (e.g., PS power pulse train 12 of FIG. 1A) to a second electrode located in the second chamber to generate a second plasma in the second chamber from a second gas flowing into the second chamber (block 624); and applying a plurality of third power pulses (e.g., BS power pulse train 14 of FIG. 1A) to a third electrode located in the second chamber to accelerate ions of the second plasma (block 626).

[0049] In FIG. 6B, another process flow 62 begins by flowing a first gas into a remote source (RS) chamber maintained at a first pressure (block 612), followed by flowing a second gas into a plasma processing chamber maintained at a second pressure lower than the first pressure (block 614). While flowing these gases, a cyclic process is performed (block 630). The cyclic process may include generating a first plasma of a first gas in the RS chamber to generate radicals and supplying the radicals to the plasma processing chamber (block 632), and performing an etching process in the plasma processing chamber in the presence of the radicals to form recesses in the substrate (block 634). These two steps (blocks 632 and 634) may be repeated cyclically to achieve a desired etching profile. In a particular embodiment, the etching process may be performed by using a set of power pulse trains (block 634), as further shown in FIG. 6C.

[0050] In FIG. 6C, the etching process (block 634) may itself be a cyclic process that includes applying a train of process source (PS) power pulses to generate a second plasma in the plasma processing chamber (block 636) and applying a train of bias source (BS) power pulses to accelerate ions of the second plasma (block 638).

[0051] 6D, an alternative process flow 54 for anisotropic etching process (block 640) begins with a passivation phase (block 642) where the surface of the substrate in the plasma processing chamber is saturated with radicals supplied from a remote source (RS) chamber. An etching phase (block 644) may then be performed by exposing the substrate in the presence of the radicals to ions, which are formed in the plasma processing chamber using a combination of process source (PS) and bias source (BS) power pulses.

[0052] FIG. 7 illustrates a plasma processing system 70 using a remote source (RS) for performing semiconductor manufacturing processes, according to various embodiments.

[0053] In Fig. 7, the plasma processing system 70 includes an RS chamber 72, a plenum 74 attached to the outlet of the RS chamber 72, and a plasma processing chamber 76 connected to the RS chamber 72 through the plenum 74. Although the RS chamber 72 is shown above the plenum 74 and the plasma processing chamber 76 in Fig. 7, other configurations are possible. For example, the RS chamber 72 may be located to the side of the plasma processing chamber 76. A first plasma 700 and a second plasma 760 may be generated in the RS chamber 72 and the plasma processing chamber 76, respectively. Gas flow within the plasma processing system 70 is indicated by block arrows.

[0054] The RS chamber 72 may be shaped like an inverted open cylinder with an RS gas inlet 702 in a top cover 708 and a radio frequency (RF) electrode 704 located on the outside of a side wall 706. The RS gas inlet 702 may be configured to introduce a first gas into the RS chamber 72. The RS gas inlet 702 may include multiple inlet ports so that multiple gases can be introduced as a gas mixture for the first gas or the composition of the first gas can be changed during the RS-mediated plasma etching process. The RF electrode 704 may be a conductive spiral wound vertically around the side wall 706 that includes a dielectric (e.g., a ceramic material). The RF electrode 704 may alternatively be located near the top cover 708 and may be shaped like a planar coil. The top cover 708 may include a conductive material with a dielectric coating on a surface facing the inside of the RS chamber 72, such as aluminum coated with alumina or yttria. Various gases (eg, argon, oxygen, sulfur hexafluoride, tetrafluoromethane, nitrogen trifluoride, etc.) may be introduced into the RS chamber 72 to form a controlled gas discharge plasma as a source of radicals.

[0055] The RF electrode 704 is coupled to an RF power source 710. The length of the conductor may be designed to be a quarter wavelength (λ / 4) or a half wavelength (λ / 2) of the RF electromagnetic oscillation of the electrode powered by the RF power source 710. In various embodiments, the oscillation frequency of the RF power may be about 15 MHz to about 500 MHz, and in certain embodiments, about 15 MHz to about 200 MHz. In one embodiment, the frequency of the RF power may be 20 MHz to 40 MHz, for example, 27 MHz. If a resonator spiral oil is used for the RF electrode 704, its number may be selected taking into account the coil length so that the coil can fully surround the sidewall 706. In an alternative embodiment, the RF electrode 704 may be made of a flat spiral coil and placed above the top cover 708. The RF electrode 704 operates in a purely inductively coupled mode to achieve about 0.01 W / cm in the RS chamber 72. 3 ~about 10W / cm 3The first plasma 700 may be configured to maintain the first plasma 700 at an RF power density of .

[0056] 7, the RS chamber 72 has an open bottom for radicals where radicals are transported from the first plasma 700 in the gas flow exiting the RS chamber 72 to a radical ballast region 728 of a plenum 74 attached to the outlet. The plenum 74 comprises a bottom wall 722, a sidewall 726 around the edge of the bottom wall 722, a rim 724 extending outward beyond the sidewall, and a radical ballast region 728 between the sidewall 726 and the bottom wall 722.

[0057] 7, the rim 724 is attached to the plasma processing chamber 76, which is disposed below the rim 724. The rim 724 extends outwardly from a sidewall 726 to cover the top of the plasma processing chamber 76 and is attached to a vertical section of a wall 734 of the plasma processing chamber 76. In various other embodiments, the rim 724 may extend partway to the edge of the plasma processing chamber 76 and be attached to the top cover of the plasma processing chamber 76, or the rim 724 and wall 734 may be one monolithic structure.

[0058] In FIG. 7, the plasma processing chamber 76 includes an annular region adjacent the sidewall 726 and extends further down into a cylindrical region adjacent the bottom wall 722. A substrate holder 732 (e.g., a circular electrostatic chuck (ESC)) may be disposed in a region near the bottom of the plasma processing chamber 76 adjacent and below the bottom wall 722 of the plenum 74. The ESC may be coated with a conductive material (e.g., a carbon-based or metal nitride-based coating) such that an electrical connection may be made to the substrate holder 732. For illustrative purposes, a substrate 500 is shown loaded onto the substrate holder 732. In one embodiment, the substrate holder 732 may be configured to accommodate a substrate 500 having a diameter of 300 mm. Thus, the plasma processing chamber 76 may have a width of 400 mm to 500 mm in one embodiment. The temperature of the substrate 500 may be maintained by a temperature controller 742. A gas outlet 736 may be disposed below the substrate holder 732 through which excess reactants and gaseous by-products may be removed from the plasma processing chamber 76. In certain embodiments, the gas outlet 736 may be disposed asymmetrically to facilitate the creation of a desired asymmetric gas flow pattern above the substrate holder 732. A gas inlet 740 may be disposed on a wall 734 of the plasma processing chamber 76 and configured to introduce a second gas into the plasma processing chamber 76. Although the RS gas inlet 702 and the gas inlet 740 are shown as single inlets, they may comprise multiple gas inlets coupled to multiple gas flow controllers. In some embodiments, an optional center / edge splitter may be used to independently adjust the gas flow rate at the center and edge of the substrate 500.

[0059] As shown in Figure 7, the substrate holder 732 can be a bottom electrode of the plasma processing chamber 76. In the illustrative example of Figure 7, the substrate holder 732 is connected to an RF bias power supply 770 configured to provide bias power (BS). A conductive circular plate near the top inside the plasma processing chamber 76 is the top electrode 752. In Figure 7, the top electrode 752 is connected to an RF power supply 750 configured to provide process source (PS) power. In some other embodiments, the top electrode can be a conductive coil located outside the plasma processing chamber 76.

[0060] The RF bias power supply 770 may be used to provide continuous wave (CW) or pulsed RF power to maintain the second plasma 760. The second plasma 760 shown between the top electrode 752 and the bottom electrode (also the substrate holder 732) illustrates a direct plasma generated near the substrate 500 in the plasma processing chamber 76 of the plasma processing system 70. Etching may be performed by exposing the substrate 500 to the second plasma 660 while powering the substrate holder 732 with the RF bias power supply 770 and the top electrode 752 with the RF power supply 750. The plasma conditions used in the process may be selected taking into account the target material of the etch. For dielectric etching (e.g., SiO2), for example, low PS power, short duration for the etching phase (t2), or low duty cycle may be used. Such plasma conditions may reduce the electron density during the etching process and minimize the cracking of chemical species useful for compensating for the loss of the etch mask.

[0061] The RS or PS power may be supplied as alternating current (AC) power in the radio frequency (RF) band (e.g., high frequency (HF), very high frequency (VHF), etc.). The BS power may be supplied as direct current (DC) power (e.g., continuous DC power, pulsed DC power, bipolar DC power, etc.) or as AC power (e.g., high frequency (HF), intermediate frequency (MF), low frequency (LF), very low frequency (VLF), etc.). In certain embodiments, the BS power may be supplied by multiple RF power sources having multiple frequencies, including, for example, HF and LF.

[0062] In various embodiments, the frequency of the PS power may be 27 MHz or more, and in certain embodiments, it may be in the very high frequency (VHF) range. For example, the frequency of the PS power may be 60 MHz, 100 MHz, or 200 MHz, which may advantageously allow for low plasma potential and low PS power. Any suitable conditions may be used for the BS. In certain embodiments, to perform dielectric etching (e.g., SiO2), RF power less than 13 MHz or DC power may be used for the BS. For conductor etching (e.g., Si), RF power having about 13 MHz may be used for the BS. Alternatively, for conductor etching, RF power having 100s kHz to 2 MHz may be used for the BS. The frequency of the BS may be selected taking into consideration the applied voltage (e.g., peak-to-peak voltage Vpp). If a low voltage is preferred to minimize undesired damage to device components, a high frequency may be selected. Conversely, if a relatively high voltage is acceptable for the process, a low frequency may be selected.

[0063] For efficient heat dissipation, the walls of the plenum 74, such as the bottom wall 722, the rim 724 and the sidewalls 726, and the walls 734 of the plasma processing chamber 76 may comprise a thermally conductive material such as aluminum, copper, etc., and are physically and thermally coupled to each other. As is known to those skilled in the art, the various conductive walls of a plasma system, such as the plasma processing system 70, may be electrically connected to a system ground (reference potential).

[0064] 7 may be provided using a variety of techniques, such as anodizing aluminum, coating with yttria, or conditioning the plasma processing chamber 76. The cover layer 721 may include one material for the walls of the plenum 74 and a different material for the walls 734 of the plasma processing chamber 76. Generally, the chemical conditions of a plasma processing chamber change during processing due to ion bombardment and chemical reactions with various radicals and gaseous by-products. The cover layer 721 provides the added benefit of reducing such fluctuations in the chemical conditions of the walls, thus further stabilizing the plasma processing environment.

[0065] The configuration of the plasma processing system 70 described above is merely exemplary. In alternative embodiments, various alternative configurations for the plasma processing system 70 may be used. For example, an inductively coupled plasma (ICP) may be used with RF source power coupled to a planar coil on a top dielectric cover, or a capacitively coupled plasma (CCP) generated using a disk-shaped top electrode in the plasma processing chamber 76, gas inlets and / or gas outlets may be coupled to the sidewalls, etc. In one embodiment, a resonator may be used and configured to operate at about 27 MHz or higher. In another embodiment, a non-resonant antenna may be used and configured to operate at about 400 kHz to about 13 MHz. Alternatively, microwave (MW) power may be used. In various embodiments, the RF power, chamber pressure, substrate temperature, gas flow rates, and other plasma process parameters may be selected according to the respective process recipe.

[0066] Although not described herein, embodiments of the present invention may be applied to remote plasma systems as well as batch systems, For example, a substrate holder may be capable of supporting multiple wafers that are spun about a central axis as they pass through different plasma zones.

[0067]

[0023] Exemplary embodiments of the present invention are summarized herein. Other embodiments can be seen throughout this specification and the claims.

[0068] Example 1. A method of etching a substrate comprising: applying a first power pulse for a first duration to a first electrode located in a first chamber to generate a first plasma from a first gas flowing into the first chamber; forming a recess in a substrate located in a second chamber, the forming comprising: supplying radicals from the first chamber into the second chamber; applying a plurality of second power pulses for a second duration to a second electrode located in the second chamber to generate a second plasma in the second chamber from a second gas flowing into the second chamber, the first chamber being pressurized at a higher pressure than the second chamber; and applying a plurality of third power pulses for a third duration to a third electrode located in the second chamber to accelerate ions of the second plasma.

[0069] Example 2. The method of example 1, further comprising maintaining a pressure in the second chamber at or below 100 mTorr while generating the first plasma and forming the recess.

[0070] Example 3. The method of example 1 or 2, further comprising maintaining a pressure in the first chamber between 100 mTorr and 5 Torr while generating the first plasma and forming the recess.

[0071] Example 4. The method of any one of Examples 1-3, wherein the pulse duration of the first power pulse is between 1 ms and 5 seconds.

[0072] Example 5. The method of any one of Examples 1-4, wherein the pulse duration of the second power pulse is between 1 μs and 20 μs.

[0073] Example 6. The method of any one of Examples 1-5, wherein the pulse duration of the third power pulse is between 5 μs and 100 μs.

[0074] Example 7. The method of any one of Examples 1-6, wherein the first duration and the second duration are overlapping.

[0075] Example 8. The method of any one of Examples 1-7, wherein the plurality of second power pulses and the plurality of third power pulses are non-overlapping.

[0076] Example 9. The method of any one of Examples 1 to 8, wherein each pulse of the plurality of second power pulses or the plurality of third power pulses includes a first edge from the first voltage level to the second voltage level, a second edge from the second voltage level to the third voltage level, and a third edge from the third voltage level to the first voltage level, wherein the first edge is separated from the second edge and the second edge is separated from the third edge.

[0077] Example 10. The method of any one of Examples 1-9, further comprising decreasing the power level for the second electrode and the power level for the third electrode during a fourth duration.

[0078] Example 11. A method for processing a substrate in a plasma processing chamber, comprising: flowing a first gas into a remote source (RS) chamber maintained at a first pressure, the RS chamber connected to the plasma processing chamber; flowing a second gas into the plasma processing chamber maintained at a second pressure, the second pressure being lower than the first pressure; and performing a cyclic process including a plurality of cycles, each cycle of the plurality of cycles including generating a first plasma of the first gas to generate radicals, supplying the radicals to the plasma processing chamber, and performing an etching process in the plasma processing chamber in the presence of the radicals to form a recess in the substrate.

[0079] Example 12. The method of example 11, wherein the second pressure is less than or equal to 100 mTorr.

[0080] Example 13. The method of example 11 or 12, wherein generating the first plasma includes applying an RS power pulse to the RS electrode, the RS power pulse having a pulse duration of 1 ms to 5 seconds.

[0081] Example 14. A method as described in any one of Examples 11 to 13, wherein the etching process includes: applying a process source (PS) power pulse train to a PS electrode to generate a second plasma in the plasma processing chamber, the PS power pulse train including a plurality of PS power pulses; and applying a bias source (BS) power pulse train to a BS electrode coupled to a substrate in the plasma processing chamber, the BS power pulse train including a plurality of BS power pulses, the BS power pulse train accelerating ions of the second plasma toward the substrate, where the ions etch the recess.

[0082] Example 15. The method of any one of Examples 11-14, wherein the PS power pulse train, the BS power pulse train, or both, have a frequency between 1 kHz and 5 kHz.

[0083] Example 16. The method of any one of Examples 11-15, wherein the PS power pulse and the BS power pulse are partially or fully overlapping.

[0084] Example 17. The method of any one of Examples 11-16, wherein the PS power pulse train, the BS power pulse train, or both, have a duty cycle of 3% to 20%.

[0085] Example 18. A plasma processing system comprising: a remote source (RS) chamber including a gas inlet, a first electrode coupled to a radio frequency (RF) power source and configured to generate a first plasma including radicals in the RS chamber, and an outlet for the radicals; a plenum attached to the outlet of the RS chamber, the plenum being made of a first thermal conductor, and a wall of the plenum including an opening for gas flow; and a plasma process chamber connected to the RS chamber through the plenum, the plasma process chamber including: a substrate holder disposed below the plenum, a gas outlet below the substrate holder, a second electrode coupled to a process power source and configured to generate a second plasma, a third electrode coupled to a first bias power source and configured to accelerate ions of the second plasma, and process chamber walls including a second thermal conductor, the process chamber walls of the process chamber being thermally coupled to the walls of the plenum.

[0086] Example 19. The plasma processing system of example 18, further comprising a microprocessor including a program executing instructions for applying a first power pulse to the first electrode for a first duration, applying a plurality of second power pulses to the second electrode for a second duration, applying a plurality of third power pulses to the third electrode for a third duration, and maintaining a pressure in the plenum higher than a pressure in the plasma processing chamber.

[0087] Example 20. A plasma processing system as described in Example 18 or 19, wherein the third electrode is further coupled to a second bias power supply, and the first bias power supply and the second bias power supply are configured to apply power pulses to the third electrode at different frequencies.

[0088] Although the present invention has been described with reference to several exemplary embodiments, this specification is not intended to be construed in a limiting sense. Various modifications and combinations of the exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to the above description. Accordingly, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. 1. A method of etching a substrate, the method comprising: generating a first plasma from a first gas flowing into a first chamber by applying a first power pulse for a first duration to a first electrode disposed in the first chamber; forming a recess in a substrate disposed in a second chamber, providing radicals from the first chamber to the second chamber; applying a plurality of second power pulses to a second electrode disposed in the second chamber for a second duration to generate a second plasma in the second chamber from a second gas flowing into the second chamber, the first chamber being pressurized at a higher pressure than the second chamber; and applying a plurality of third power pulses to a third electrode disposed in the second chamber for a third duration to accelerate ions of the second plasma. and The method comprising:

2. 10. The method of claim 1, further comprising the step of maintaining a pressure in the second chamber at or below 100 mTorr during the steps of generating the first plasma and forming the recess.

3. 10. The method of claim 1, further comprising the step of maintaining a pressure in the first chamber between 100 mTorr and 5 Torr during the steps of generating the first plasma and forming the recess.

4. The method of claim 1 , wherein the pulse duration of the first power pulse is between 1 ms and 5 seconds.

5. The method of claim 1 , wherein the pulse duration of the second power pulse is between 1 μs and 20 μs.

6. The method of claim 1 , wherein a pulse duration of the third power pulse is between 5 μs and 100 μs.

7. The method of claim 1 , wherein the first duration and the second duration are overlapping.

8. The method of claim 1 , wherein the plurality of second power pulses and the plurality of third power pulses are non-overlapping.

9. each pulse in the plurality of second power pulses or the plurality of third power pulses has a first edge from a first voltage level to a second voltage level, a second edge from the second voltage level to a third voltage level, and a third edge from the third voltage level to the first voltage level; The method of claim 1 , wherein the first edge is separated from the second edge, and the second edge is separated from the third edge.

10. The method of claim 1 , further comprising decreasing a power level for the second electrode and a power level for the third electrode during a fourth duration.

11. 1. A method for processing a substrate in a plasma processing chamber, the method comprising: flowing a first gas into a remote source (RS) chamber maintained at a first pressure, the RS chamber being connected to a plasma processing chamber; flowing a second gas into the plasma processing chamber maintained at a second pressure, the second pressure being less than the first pressure; Conducting a cyclic process comprising a plurality of cycles, each cycle of the plurality of cycles comprising: generating a first plasma of the first gas to generate radicals; providing the radicals to the plasma processing chamber; and performing an etching process in the plasma processing chamber in the presence of the radicals to form a recess in the substrate; and The method comprising:

12. The method of claim 11 , wherein the second pressure is less than or equal to 100 mTorr.

13. generating the first plasma includes applying an RS power pulse to an RS electrode; The method of claim 11 , wherein the RS power pulse has a pulse duration between 1 ms and 5 seconds.

14. The etching process comprises: applying a process source (PS) power pulse train to a PS electrode to generate a second plasma in the plasma processing chamber, the PS power pulse train including a plurality of PS power pulses; applying a bias source (BS) power pulse train to a BS electrode coupled to the substrate in the plasma processing chamber, the BS power pulse train having a plurality of BS power pulses, the BS power pulse train accelerating ions of the second plasma towards the substrate, where the ions etch the recess; 12. The method of claim 11, having the following structure:

15. 15. The method of claim 14, wherein the PS power pulse train, the BS power pulse train, or both, have a frequency between 1 kHz and 5 kHz.

16. The method of claim 14 , wherein the PS power pulse and the BS power pulse are partially or fully overlapping.

17. The method of claim 14 , wherein the PS power pulse train, the BS power pulse train, or both have a duty cycle between 3% and 20%.

18. 1. A plasma processing system comprising: a remote source (RS) chamber having a gas inlet, a first electrode coupled to a radio frequency (RF) power source configured to generate a first plasma comprising radicals in the RS chamber, and an outlet for the radicals; a plenum attached to the outlet of the RS chamber, the plenum is comprised of a first thermal conductor; the plenum wall has gas flow openings; The plenum and a plasma processing chamber connected to the RS chamber through the plenum, the plasma processing chamber comprising: a substrate holder disposed below the plenum; a gas outlet below the substrate holder; a second electrode coupled to the process power supply and configured to generate a second plasma; a third electrode coupled to a first bias power supply and configured to accelerate ions of the second plasma; and a process chamber wall including a second thermal conductor, the process chamber wall of the process chamber being thermally coupled to the wall of the plenum; a plasma process chamber having a A plasma processing system comprising:

19. Further, the device has a microprocessor, The microprocessor includes: applying a first power pulse to the first electrode for a first duration; applying a plurality of second power pulses to the second electrode for a second duration; applying a plurality of third power pulses to the third electrode for a third duration; maintaining a pressure in the plenum greater than a pressure in a plasma processing chamber; 20. The plasma processing system of claim 18, further comprising a program for executing instructions for:

20. the third electrode is further coupled to a second bias power supply; 20. The plasma processing system of claim 19, wherein the first bias power supply and the second bias power supply are configured to apply power pulses to the third electrode at different frequencies.

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