Methods of plasma processing using a pulsed electron beam

Abstract

A plasma processing method includes continuously supplying a gas to a processing chamber and continuously supplying AC source power to a source power coupling element during a first duration. The AC source power generates plasma in the processing chamber. The method further includes: applying a first negative bias voltage to an electron source electrode during a second duration while the gas and AC source power are being supplied, and removing the first negative bias voltage from the electron source electrode during a third duration at the end of the second duration to stop electron beam generation. The first negative bias voltage generates an electron beam guided to a substrate holder. The method also includes applying a second negative bias voltage to the substrate holder while the gas and AC source power are being supplied. The first duration is equal to the sum of the second and third durations.

Description

[Technical Field]

[0001] [Cross-reference to related applications] This application claims priority and filing date benefit to U.S. nonprovisional patent application No. 16 / 737,716, filed January 8, 2020, which is incorporated herein by reference in its entirety.

[0002] The present invention generally relates to a method of plasma treatment, and in particular embodiments to a system, apparatus and method of plasma treatment using a pulsed electron beam. [Previous Technology]

[0003] The formation of components on and within microelectronic workpieces may involve a series 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, processing equipment and methods capable of reducing feature size while maintaining structural integrity are desirable for various patterning processes. With the densification and verticalization of device structures, the need for precision material handling is becoming increasingly urgent.

[0004] Atomic precision in plasma processing is useful for contour control in various plasma processes. However, due to limitations in gas switching speed, conventional plasma processes may not be able to deposit and / or etch films with the precision of a single layer. Therefore, plasma processing methods that include means of controlling the deposition / etching process at a faster timescale than the gas switching speed (e.g., at the timescale associated with the growth of a single monolayer film) may be needed. [Summary of the Invention]

[0005] According to an embodiment of the present invention, a plasma processing method includes: continuously supplying a gas to a processing chamber during a first duration, and continuously supplying alternating current (AC) source power to a source power coupling element during the first duration while supplying the gas. The method further includes: applying a first negative bias voltage to an electron source electrode during a second duration while supplying the gas and the AC source power, and removing the first negative bias voltage from the electron source electrode during a third duration at the end of the second duration to stop the generation of the electron beam. The first negative bias voltage generates an electron beam guided to a substrate holder. The method also includes: applying a second negative bias voltage to the substrate holder while supplying the gas and the AC source power. The first duration is equal to the sum of the second duration and the third duration. The method can be performed cyclically.

[0006] According to another embodiment of the present invention, a plasma etching method includes: generating an inductively coupled plasma in a processing chamber, and forming a first polymer layer on the first surface using a first electron beam guided to a first surface of a substrate disposed in the processing chamber. The first electron beam is generated at a second surface of an electron source electrode facing the first surface by means of a first negative bias during a first duration. The method further includes: after the first duration, accelerating positive ions of the inductively coupled plasma toward the first surface by means of a second negative bias applied during a second duration, thereby etching the first polymer layer and the first surface of the substrate.

[0007] According to yet another embodiment of the present invention, a plasma processing apparatus includes: a processing chamber; a first direct current (DC) power supply node; an electron source electrode coupled to the first DC power supply node and including a first surface; a substrate holder disposed in the processing chamber; and a radio frequency (RF) source power coupling element disposed outside the processing chamber, the RF source power coupling element being configured to inductively couple RF source power to plasma generated in the processing chamber. The electron source electrode is configured to generate a pulsed electron beam in the processing chamber using a first pulsed DC bias potential supplied to the electron source electrode by the first DC power supply node. The first surface is located within the processing chamber. The substrate holder includes a second surface facing the first surface.

Implementation Method

[0008] The following discusses in detail the generation and use of various embodiments. However, it should be understood that the various embodiments described herein can be applied to various specific situations. The specific embodiments described are merely illustrative of specific ways of generating and using various embodiments and should not be construed as limited thereto.

[0009] Precision plasma processing (e.g., atomic layer etching (ALE) and atomic layer deposition (ALD) processes) can utilize surface modification techniques to enhance control over subsequent reactions at the substrate. Conventional surface modification techniques can be time-consuming and imprecise. For example, the gas injection and process chamber evacuation times for initiating and stopping surface chemical reactions may require undesirablely long timescales to achieve the desired results. Therefore, accelerating conventional surface modification steps is possible, but only at the expense of precision.

[0010] During plasma processing, source power can be coupled to a source power coupling element (e.g., a coil of a helical resonator) to generate plasma. The plasma may contain reactive and non-reactive species, such as electrons, ions, and free radicals. Bias power can be applied to a substrate holder to couple energy to the plasma species at the substrate supported by the substrate holder. An electron beam can be used to modulate plasma characteristics and initiate a reaction at the substrate surface. Advanced pulse technology (APT), which modulates the application of one or more of the source power, bias power, electron beam generation, and gas injection during plasma processing, advantageously enables precise control at the substrate.

[0011] Electron beam-mediated processing can be used to induce chemical reactions both within the host plasma and at the substrate surface. Electrons striking the substrate surface (e.g., ballistic electrons) can create dangling bonds and induce chemical reactions (e.g., polymer growth) at the substrate surface. Electrons may also penetrate deep into feature areas of the substrate, depending on the electron energy and the substrate material. An appropriate potential gradient can be used to slow down the electrons in the electron beam passing through the generated plasma, so that some or all of the electrons in the beam interact within the host plasma. These interactions can induce chemical reactions, such as polymerization, within the host plasma.

[0012] An electron beam can be generated using an existing plasma generated in the processing chamber. The existing plasma can be any suitable type, such as inductively coupled plasma (ICP), capacitively coupled plasma (CCP), surface wave plasma (SWP), wave-heated plasma, etc. The plasma can be maintained by an AC power source (e.g., an RF power source, a VHF source, etc.). A DC bias can be applied to a conductive surface within the processing chamber to generate an electron beam from the plasma. For example, a negative DC bias can be applied to a conductive surface near an existing plasma, attracting positively charged ions to the conductive surface, where secondary emission caused by ion bombardment generates an electron beam. A pulsed DC bias or a bipolar DC bias can be applied to the dielectric surface, provided the pulse duration is shorter than the time it takes for the plasma charged species flux to charge the surface and eliminate the electric field in front of the dielectric.

[0013] Due to the high energy of electrons, the generated electron beam can be substantially perpendicular to the conductive surface. The generation of the electron beam can be directly controlled by a DC bias voltage. In other words, when a DC bias voltage is applied, the electron beam can be substantially "started" instantaneously. Similarly, when the DC bias voltage is removed, the electron beam can be substantially "stopped" instantaneously.

[0014] Conventional methods of achieving chemical processes (such as polymer growth) on substrate surfaces using gas switching can be slow and imprecise. Electron beam-mediated processing advantageously provides an alternative way to obtain similar or improved results without the drawbacks associated with gas switching. For example, gas switching is not easily implemented and cannot be switched on the timescale of monolayer polymer growth. In other words, gas switching may be limited to a timescale longer than that associated with the growth of a single monolayer or several monolayers of polymer. However, using a DC bias electrode adjacent to an existing plasma, it is advantageous to start and stop the electron beam on the same timescale as (or even faster than) the growth of a single monolayer or several monolayers of polymer. Due to the immediacy of the relationship between the DC bias and the electron beam, the polymerization process can be precisely controlled. For example, polymer generation at the substrate or in the bulk plasma can be essentially digital (i.e., the "on" and "off" states of polymer growth). The polymer generation rate can also be relatively low when the electron beam is off and relatively high when the electron beam is on (i.e., the "high" and "low" states of polymer growth).

[0015] In many embodiments, a plasma processing method includes continuously supplying gas to a processing chamber and supplying AC source power to a source power coupling element for a duration. The AC source power generates plasma in the processing chamber. While the gas and AC source power are being supplied, a first negative bias is applied to an electron source electrode. The first negative bias generates an electron beam that is guided to a substrate holder. Then, while the gas and AC power are still being supplied, the first negative bias is removed from the electron source electrode. The removal of the first negative bias stops the generation of the electron beam. During part or all of the duration, a second negative bias (e.g., a DC self-bias generated by the AC power) is applied to the substrate holder.

[0016] The AC source power can be RF source power, which is inductively coupled to plasma. The source power coupling element can be, for example, a helical coil or a planar coil. The substrate can be held in place by a substrate holder. The substrate may include a surface facing the electron beam. In one embodiment, the method is a plasma etching process. During the plasma etching process, a polymer layer is formed on the substrate surface using an electron beam, and then the polymer layer and the substrate surface are etched together using plasma ions.

[0017] The plasma processing methods described herein can advantageously achieve single-layer-level control over the plasma processing. For example, these methods can be advantageously applied to various plasma processes involving high aspect ratio features and / or high precision requirements, such as patterning, ALD, quasi-ALD, ALE, quasi-ALE, self-aligned contact window (SAC) etching, high aspect ratio contact window (HARC) etching, and other processes for forming contact windows, NAND structures, dynamic random access memory (DRAM), etc. These methods can also advantageously improve contour control during plasma processing. Another possible advantage of the embodiments is that the desired chemical reaction can be preferentially activated on the horizontal surface of the substrate. These methods can further advantageously facilitate cyclic plasma processing with little or no gas switching. Another possible advantage of the embodiments described herein is that atomic-level control can be provided during plasma processing even in the absence of self-limiting chemical reactions. The methods can also advantageously improve spatial control in area-selective etching processes (e.g., SAC processing or patterning).

[0018] The following embodiments describe various systems, apparatuses, and methods for plasma processing (especially plasma processing using pulsed electron beams). These embodiments are described below. Figures 1 and 2 illustrate two embodiments of a plasma processing apparatus including an electron source electrode and a source power coupling element. Figure 3 illustrates a schematic timing diagram of an embodiment of a plasma processing method including a DC pulse and a bias pulse. Figure 4 illustrates an embodiment of a plasma etching method. Figure 5 illustrates another embodiment of a plasma processing method using DC pulses and bias pulses. Figure 6 illustrates an embodiment of a plasma processing system. Figures 7 and 8 illustrate two implementations of plasma processing, the second being a plasma etching process.

[0019] Figure 1 shows a schematic diagram of an exemplary plasma processing apparatus according to the present invention, including an electronic source electrode and a source power coupling element.

[0020] Referring to FIG1, the plasma processing apparatus 100 includes a processing chamber 10 and a source power coupling element 112. The processing chamber 10 contains a conductive material and may be grounded at all or some of its conductive surfaces. In some embodiments, depending on the process application, some surfaces of the processing chamber 10 may be coated with an etch-resistant dielectric material, such as Y2O3, anodic aluminum oxide, or other compounds. In one embodiment, the source power coupling element 112 is disposed outside the processing chamber 10. Alternatively, the source power coupling element 112 may be disposed inside the processing chamber 10. The source power coupling element 112 receives source power SP, which in many embodiments may be AC ​​source power. The source power SP is coupled to the processing chamber 10 and generates plasma 20 within the processing chamber 10.

[0021] In many embodiments, the source power coupling element 112 is an RF coupling element. In one embodiment, the source power coupling element 112 is a coaxial ICP coil as illustrated. The source power coupling element 112 can be an induction coil having any suitable geometry, such as a cylindrical (e.g., spiral) coil, a planar (e.g., worm) coil, etc. In some embodiments, in a spiral resonator configuration, the source power coupling element 112 may be surrounded by a grounded cylindrical shield. Although shown as surrounding the sidewall of the processing chamber 10, the source power coupling element 112 may also be disposed above or inside the processing chamber 10. For example, the source power coupling element 112 may also be an electrode disposed in the processing chamber 10 in a capacitively coupled configuration.

[0022] Plasma 20 may comprise a mixture of electrons 21, ions, and free radicals 27. The ions may be positively or negatively charged. For example, plasma 20 may comprise electrons 21 and positively charged ions 25. Plasma 20 may be any suitable type of plasma. In one embodiment, plasma 20 is an ICP. In other embodiments, plasma 20 may be a CCP, SWP, microwave-heated plasma, and others. Plasma 20 may be generated near the electron source electrode 14.

[0023] The electron source electrode 14 includes an emitter surface 15 disposed within the processing chamber 10. The electron source electrode 14 may be disposed entirely within the processing chamber 10 (as shown) or partially within the processing chamber. A DC bias voltage VDC is applied to the electron source electrode 14 to generate an electron beam 29 containing ballistic electrons 22 within the processing chamber 10. In one embodiment, the DC bias voltage VDC is a negative DC bias voltage. The DC bias voltage VDC may be continuous, pulsed, or pulsed bipolar. The emitter surface 15 of the electron source electrode 14 can be used as an electron emitter by attracting ions 25 of the plasma 20 to strike the emitter surface 15 and generate ballistic electrons 22. The ballistic electrons 22 may have energy significantly higher than the plasma potential, thereby allowing them to pass through the plasma 20 substantially unimpeded.

[0024] The electron beam 29 may be substantially perpendicular to the emitter surface 15. For example, the value of the DC bias voltage VDC may be sufficient to impart a substantially perpendicular velocity to the ballistic electrons 22 of the electron beam 29. As shown, the electron beam 29 is guided by a substrate holder 16 disposed in the processing chamber 10. The substrate holder 16 may be, for example, an electrostatic chuck. The substrate 140 may be supported by the substrate holder 16. The substrate 140 includes opposing surfaces 19 that can receive incident ballistic electrons 22 passing through the plasma 20.

[0025] Optionally, AC power may also be applied to the electron source electrode 14. The optional AC power may be used as an additional source for the plasma 20. In one embodiment, the optional AC power is RF power. In another embodiment, the optional AC power is VHF power.

[0026] The substrate holder 16 receives a bias voltage, which may be an RF bias voltage VRF, as shown. For example, the RF bias voltage VRF can prevent the substrate 140 from becoming charged under continuous voltage offset. In many embodiments, the RF bias voltage VRF is negative. The RF bias voltage VRF can accelerate positively charged ions 25 or other charged species toward the opposite surface 19. The processing chamber 10 may include a bias return path (another DC surface, a ground surface, or a surface reverse-biased) at the substrate holder 16. For example, the return path may be adjacent to the electron source electrode 14 or another suitable location, which may depend on the specific design requirements of a particular embodiment.

[0027] The behavior of electrons in the electron beam 29 (e.g., path, energy, etc.) may depend on the potential characteristics between the electron source electrode 14 and the substrate holder 16. For example, at least three potentials may affect the behavior of the electron beam 29. These three potentials may be the DC bias voltage VDC, the plasma potential, and the RF bias voltage VRF. The relationship between these potentials may affect the energy of electrons in the electron beam 29 when they are located in the plasma 20, thereby creating a distinctive qualitative state.

[0028] As shown in the figure, electrons in electron beam 29 can be considered to be in three different states (ballistic electrons 22, captured electrons 23, and captured and dumped electrons 24). Ballistic electrons 22 are generated when the DC bias voltage VDC is much greater than the peak-to-peak average combination of the plasma potential and the RF bias voltage VRF. The energy of the ballistic electrons 22 can be large enough to reduce or effectively eliminate the interaction cross-section between the ballistic electrons 22 and the species in the plasma 20. Therefore, the ballistic electrons 22 can pass through the plasma substantially unimpeded and reach the opposing surface 19 with sufficient energy to break the bond and / or change the reactivity at the substrate 140.

[0029] When the DC bias voltage VDC is much smaller than the peak-to-peak average combination of the plasma potential and the RF bias voltage VRF, trapped electrons 23 can be generated. In this state, the energy of the electrons in the electron beam 29 is sufficiently small, thus being impeded and "trapped" within the plasma 20. The trapped electrons 23 can have a large interaction cross-section with the species in the plasma 20, thus causing numerous collisions with the neutral gas. Furthermore, the trapped electrons 23 can be slowed down so that their energy is comparable to the plasma potential.

[0030] The captured and dumped electrons 24 can be considered as being in a "hybrid state" between ballistic and captured states. Captured and dumped electrons 24 are generated when the combination of DC bias VDC and plasma potential and RF bias VRF is comparable (e.g., slightly higher). In this state, the electrons of the electron beam 29 have a non-negligible interaction cross-section with the species in the plasma 20. In other words, the captured and dumped electrons 24 may have sufficient energy to pass through the plasma 20 without interacting, or maintain a trajectory toward the substrate holder 16 even after interacting within the plasma 20. In the captured and dumped state, the electrons of the electron beam 29 may have energy such that a portion of the electrons pass directly through the plasma 20, a portion are completely captured in the plasma 20, and the remainder interact and then leave the plasma 20. As a result, the angular distribution of electrons passing through the plasma 20 in the captured and dumped state is higher than the angular distribution of electrons passing through the plasma 20 in the ballistic state.

[0031] In one example of a ballistic state, the DC bias voltage VDC may be approximately 500 V, the RF bias voltage VRF may be off, and the plasma potential may be approximately 30 V. In this case, a significant portion of the electrons in the electron beam 29 will be ballistic electrons 22, which arrive at the opposing surface 19 with energies close to 470 V. In this state, there may be virtually no interaction between the electron beam 29 and the plasma 20. However, the ballistic electrons 22 striking the opposing surface 19 of the substrate 140 may have sufficient energy to generate dangling bonds and induce chemical reactions (e.g., polymer formation).

[0032] In one example of the trapped state, the DC bias voltage VDC can be approximately 500 V, the plasma potential can be approximately 30 V, and the inter-peak RF bias voltage VRF can be approximately 650 V. In this state, a significant portion of the electrons in the electron beam 29 will remain in the plasma as trapped electrons 23. For example, trapped electrons 23 can promote host plasma polymerization (e.g., fluorocarbon fragments). The dissociation of plasma 20 can also be controlled using trapped electrons 23. For example, a weak plasma source may have a lower degree of dissociation, thereby allowing polymerization to be controlled by the electron beam 29 rather than the source power.

[0033] According to an embodiment of the present invention, FIG2 shows a schematic diagram of another exemplary plasma processing apparatus including an electron source electrode and a source power coupling element. The plasma processing apparatus of FIG2 may be an alternative configuration (e.g., having the same features that may be configured differently) to other plasma processing apparatuses described herein (e.g., plasma processing apparatus 100 of FIG1). Elements labeled in a similar manner may be as described above.

[0034] Referring to FIG2, the plasma processing apparatus 200 includes an electron source electrode 14 and a substrate holder 16 disposed in the processing chamber 10, all of which are as described above. In contrast to the plasma processing apparatus 100 shown in FIG1, the plasma processing apparatus 200 includes a source power coupling element 212 disposed outside and above the processing chamber 10. The source power coupling element 212 may be a specific embodiment of the source power coupling element 112 of FIG1. ​​The source power coupling element 212 may be a planar induction coil.

[0035] In one embodiment, the source power coupling element 212 is a pancake-shaped induction coil disposed above the processing chamber 10 in a pancake ICP configuration. A DC-biased Faraday cage may be disposed between the pancake-shaped induction coil and the electronic source electrode 14 to reduce or eliminate coupling between them. Another method to suppress current coupling between the coil and other metal surfaces may be to include grooves in the surface of the electronic source electrode 14 facing the coil to increase impedance. A sufficiently rapid pulsed DC bias VDC may be applied to prevent the quartz window from becoming charged. Alternatively or additionally, the electronic source electrode 14 may include structural decoupling mechanisms such as slots to prevent image current. The electronic source electrode 14 may also include a DC surface configured to act as a Faraday shield.

[0036] The coupling between the source power coupling element 212 and the electronic source electrode 14 can also be further reduced by placing the source power coupling electrode 212 outside the outer diameter 65 of the electronic source electrode 14, as shown in the figure. In other words, the inner diameter 66 of the source power coupling electrode 212 can be larger than the outer diameter 65.

[0037] According to an embodiment of the present invention, FIG3 shows a schematic timing diagram of an exemplary method of plasma processing including DC pulses and bias pulses. This schematic timing diagram may represent a plasma processing method performed by any of the plasma processing apparatus or plasma processing system described herein (e.g., plasma processing apparatus 100 of FIG1 or plasma processing apparatus 200 of FIG2).

[0038] Referring to FIG3, the schematic timing diagram 300 includes a source pulse 334 indicating that source power SP is applied to the source power coupling electrode, a DC pulse 332 indicating that DC power is applied to the electron source electrode, and a bias pulse 336 indicating that bias power BP is applied to the substrate holder. The schematic timing diagram 300 may also include a gas pulse 338 indicating that gas is injected into the processing chamber. For example, as shown, the gas pulse 338 may be continuous because the gas pulse can in principle be on a relatively long time scale (at least on the order of residence time). The pulses can be applied cyclically to the plasma processing apparatus during plasma processing. For example, the pulses can be applied periodically so that the pulse pattern repeats with the pulse period 331, as shown.

[0039] As shown, the source power SP can be applied continuously. For example, the source pulse 334 may have a source pulse duration 335 equal to the pulse period 331. Alternatively or additionally, the source power SP may be pulsed so that the source pulse duration is shorter than the pulse period 331. Similarly, gas may be continuously injected with a gas pulse duration 339 equal to the pulse period 331, or it may be adjusted within the pulse period 331. In one embodiment, the source power SP and gas are applied continuously during plasma treatment.

[0040] DC power is initiated during a portion of the pulse period 331. Specifically, the DC pulse 332 has a DC pulse duration 333 shorter than the pulse period 331. For example, the DC pulse duration 333 may advantageously be less than the gas switching speed achievable in conventional plasma processing. The DC pulse 332 is used to generate an electron beam in the processing chamber. The electron beam is generated substantially instantaneously (i.e., "initiated") when DC power is applied and is terminated substantially instantaneously (i.e., "off") when DC power is removed. For example, when the DC power is off, the electron source electrode can be coupled to ground potential.

[0041] The DC pulse duration 333 can be approximately the gas residence time. In many embodiments, the DC pulse duration 333 is shorter than about 500 ms. For example, the DC pulse duration 333 can be between about 100 ms and about 3 s. In one embodiment, the DC pulse duration 333 is about 100 ms. In one embodiment, the DC pulse duration 333 is about 1 ms. In some embodiments, the DC pulse duration 333 can also be greater than 3 s.

[0042] The bias power BP can be continuously applied or activated during a portion of the pulse period 331. As previously mentioned, the bias power BP can be RF power with a DC offset. In many embodiments, the bias pulse 336 has a bias pulse duration 337 shorter than the pulse period 331. In some embodiments, each of the bias pulses 336 begins after the DC pulse duration 333 within each pulse period 331. For example, each of the bias pulses 336 may begin immediately after the end of the corresponding DC pulse 332 (as shown), or it may be delayed. Furthermore, the bias pulse duration 337 does not necessarily extend to the end of each pulse period 331. For example, there may be intervals before and / or after each of the bias pulses 336 where both the DC power and the bias power BP are off.

[0043] According to an embodiment of the present invention, FIG4 shows a schematic diagram of an exemplary method of plasma etching, which includes forming a polymer layer on a substrate using an electron beam and etching the polymer layer and the substrate together. The plasma etching method may be a specific embodiment of an exemplary method of plasma processing as described herein, such as the plasma processing method of FIG3.

[0044] Referring to FIG4, the plasma etching method 400 includes a beam initiation phase 41 and a beam deactivation phase 47. During the beam initiation phase 41, an electron beam is generated in the processing chamber and directed toward the substrate 440. During the beam deactivation phase 47, the electron beam is deactivated and positively charged ions 25 are attracted toward the substrate 440. The plasma etching method 400 can be applied to any suitable etching process, including specific types of etching processes. In one embodiment, the plasma etching method may be a SAC etching process. Alternatively, the plasma etching method 400 may be a HARC etching process.

[0045] Various features may be included within the substrate 440, such as a high aspect ratio feature 44, which includes a lateral dimension 63 much smaller than the vertical dimension 61. For example, the high aspect ratio feature 44 may be a trench, a hole, or any suitable shape of an area having a smaller lateral dimension and a larger vertical dimension. In many embodiments, the aspect ratio of the high aspect ratio feature 44 (e.g., vertical dimension 61 divided by lateral dimension 63) is greater than about 25. In some embodiments, the aspect ratio of the high aspect ratio feature 44 is greater than about 50, and in one embodiment it is about 100.

[0046] A mask 43 may be disposed over the body material 42 of the substrate 440. A thin conformal layer 45 may be disposed on various surfaces of the body material 42, such as the sidewalls and bottom surface of the high aspect ratio feature 44 shown. In one embodiment, the thin conformal layer 45 is a thin nitride layer. The high aspect ratio feature 44 may be filled with a filler layer 46. The filler layer 46 may be a target material to be etched during plasma etching. In one embodiment, the filler layer 46 is an oxide filler layer.

[0047] During the beam initiation phase 41, ballistic electrons 22 impact the exposed surfaces of the substrate 440. The ballistic electrons 22 may be substantially perpendicular to horizontal surfaces (such as the exposed surfaces of the shield 43, the thin conformal layer 45, and the filler layer 46). Positively charged ions 25 are accelerated away from the substrate 440 during the beam initiation phase 41, while the movement of free radicals 27 (e.g., uncharged species) may be dominated by diffusion effects.

[0048] Due to the incident ballistic electrons 22, the polymer layer 48 can be grown on the surface of the substrate 440 during the beam initiation phase 41. The vertical characteristics of the ballistic electrons 22 can advantageously promote polymer growth, primarily or entirely on the horizontal surface of the substrate 440, as shown. The polymer layer 48 can be used to protect underlying materials not specifically marked by plasma etching, such as the mask 43 and the thin conformal layer 45. For example, the geometry (e.g., corners) of the thin conformal layer 45 can be protected by the polymer layer 48.

[0049] The growth of the polymer layer 48 can be tightly controlled by applying a DC bias to the electron source electrode. For example, even after the polymer has grown on the thin conformal layer 45 and the filler layer 46, the high aspect ratio feature 44 can still be advantageously kept on. In contrast, conventional plasma etching processes may disadvantageously "pinch off" the high aspect ratio feature, resulting in a reduction in the etching efficiency of the material within the feature.

[0050] After the beam initiation phase 41, the electron beam containing ballistic electrons 22 is turned off (e.g., by removing the DC bias from the electron source electrode). Then, the exposed surface of the substrate 440 is etched during the beam shutdown phase 47. Therefore, the beam initiation phase 41 can be considered as a DC bias phase or a ballistic electron mode, while the beam shutdown phase 47 can be considered as an etching phase or a high-energy ion phase of the plasma etching method 400. For example, bias power can be applied to the substrate holder to accelerate positively charged ions 25 to the substrate 440 during the beam shutdown phase 47. The polymer layer 48 and the filler layer 46 are etched during the beam shutdown phase 47.

[0051] Suitable chemicals may be present between the polymer layer 48 and the filler layer 46 so that the amount of filler layer 46 removed is controllable. The amount of polymer grown on the filler layer 46 can be advantageously controlled by the duration of the beam start-up phase 41. Thus, the desired etching depth 49 of the filler layer 46 can be achieved during the beam shut-off phase 47. In many embodiments, the etching depth 49 is less than three monolayers of filler layer 46. In one embodiment, the etching depth 49 is substantially one monolayer of filler layer 46. The beam start-up phase 41 and beam shut-off phase 47 can be performed cyclically to precisely etch the filler layer 46 without substantially altering the mask 43 and / or the thin conformal layer 45.

[0052] The plasma etching method 400 can advantageously induce surface chemical reactions on the substrate 440 without requiring a gas switching step. The duration of the beam initiation phase 41 can advantageously be similar to or the same as the time required to grow a single polymer monolayer (e.g., on the filler layer 46). For example, the duration of the beam initiation phase 41 can be comparable to the residence time of the gas on the substrate 440.

[0053] In one particular example, fluorocarbons (which can be used to etch oxides (e.g., in a SAC etching process)) can grow on their own and cause geometric expansion of the protective nitride layer (e.g., at corners) in conventional plasma etching processes. Such deviations from the underlying nitride geometry can cause problems near small-sized openings (e.g., when the lateral dimension 63 is approximately 10–20 nm) (e.g., for high aspect ratio feature 44). For example, uncontrolled additional fluorocarbon polymerization during conventional plasma etching processes can clog the openings of the high aspect ratio feature 44.

[0054] Because the nitride layer masks the oxide layer, these blocked features result in obstruction of the desired oxide etching during the etching stage. However, in plasma etching method 400 and other embodiments of plasma processing, digital (or near-digital) control of the electron beam (and the resulting surface chemistry and / or bulk plasma chemistry) on a monolayer formation timescale can advantageously reduce or eliminate geometrical artifacts, thereby preventing blockage of high aspect ratio features 44. These and similar advantages can also be largely achieved in plasma processing such as ALD, quasi-ALD, ALE, quasi-ALE, HARC, NAND device formation, DRAM device formation, etc.

[0055] According to an embodiment of the present invention, FIG5 shows a schematic timing diagram of another exemplary method of plasma processing including DC pulses and bias pulses. The schematic timing diagram of FIG5 may represent a plasma processing method performed by any of the plasma processing apparatus or plasma processing system described herein (e.g., plasma processing apparatus 100 of FIG1 or plasma processing apparatus 200 of FIG2).

[0056] Referring to FIG5, the schematic timing diagram 500 may be a specific embodiment of the schematic timing diagram 300 of FIG3, wherein the bias power BP is applied simultaneously with the DC power. As shown, the schematic timing diagram 500 includes a source pulse 534 with a source pulse duration of 535, a DC pulse 532 with a DC pulse duration of 533, and a bias pulse 536 with a bias pulse duration of 537. Gas can also be injected in the form of a gas pulse 538 with a gas pulse duration of 539.

[0057] The duration of the DC pulse is less than the pulse period 531, while the duration of the source pulse 535 and the duration of the bias pulse 537 are equal to the pulse period 531. Alternatively, a bias pulse 536 may be applied during the DC pulse 532, but the bias pulse 536 may still be shorter than the pulse period 531 (i.e., it ends before the end of each pulse period 531 and / or is delayed relative to the start of each pulse period 531). As another alternative, multiple bias pulses 536 may be applied during each pulse period 531. For example, one bias pulse may be delivered simultaneously with the DC pulse, while another bias pulse may be delivered when the DC power is off.

[0058] Applying a bias power BP during the DC pulse 532 can advantageously be used to modulate the state of electrons in the generated electron beam and to adjust the chemical interactions induced within the bulk plasma and / or at the substrate surface. It should be noted that the bias power BP during DC power startup may be the same as or different from the bias power BP during DC power shutdown.

[0059] According to an embodiment of the present invention, FIG6 shows a schematic diagram of an exemplary plasma processing system, which includes an electron source electrode coupled to a DC bias supply node and a source power coupling element coupled to a source power supply node. The plasma processing system of FIG6 may include any of the plasma processing devices as described herein, such as plasma processing device 100 of FIG1 or plasma processing device 200 of FIG2. Components labeled in a similar manner may be as described above.

[0060] Referring to FIG6, the plasma processing system 600 includes an electron source electrode 14 having an emitter surface 15 disposed in a processing chamber 10. The electron source electrode 14 is coupled to a DC bias generator circuit 52, which is further coupled to a DC bias supply node 53, which is coupled to ground 50. The electron source electrode 14 may be coupled to a selective AC power supply node 59 via an optional AC power generator circuit 58. The selective AC power supply node 59 may be coupled to a selective ground 51, which in some embodiments may be ground 50. As previously described, the AC power supply node 59 may supply RF power, VHF power, or any other suitable AC power.

[0061] The plasma processing system 600 also includes a source power coupling element 112 coupled to a source power supply node 55 via a source power generator circuit 54, and a substrate holder 16 coupled to a bias power supply node 57 via a bias power generator circuit 56. The source power supply node 55 and the bias power supply node 57 may also be grounded via a ground 50 or an isolated ground.

[0062] Although shown as separate circuits, one or more of these generator circuits and / or supply nodes may be combined as needed, depending on the specific design parameters of a given application. Furthermore, some or all of the surfaces of the processing chamber 10 may be grounded. Such grounding may be a common ground, a reference ground, or a reference potential.

[0063] FIG7 illustrates an exemplary method of plasma treatment according to an embodiment of the present invention. The method of FIG7 can be performed by any of the plasma treatment apparatus or plasma treatment system described herein (e.g., plasma treatment apparatus 100 of FIG1, plasma treatment apparatus 200 of FIG2, or plasma treatment apparatus 600 of FIG6). Furthermore, the schematic timing diagrams described herein (e.g., schematic timing diagram 300 of FIG3 or schematic timing diagram 500 of FIG5) may correspond to some or all of the portions of the method of FIG7.

[0064] Referring to FIG7, method 700 includes a step 701 of continuously supplying gas to a processing chamber, which is performed simultaneously with a step 702 of continuously supplying AC source power to a source power coupling element, the AC source power generating plasma in the processing chamber. For example, steps 701 and 702 may be performed during a first duration.

[0065] While performing steps 701 and 702, method 700 further includes performing step 703, which applies a first negative bias voltage to the electron source electrode. The first negative bias voltage generates an electron beam guided to the substrate holder. The first negative bias voltage is applied during a second duration shorter than the first duration.

[0066] After performing step 703, step 704 is performed, which removes the first negative bias voltage from the electron source electrode to stop the generation of the electron beam. Step 704 may have a third duration shorter than the first duration. In one embodiment, the first duration is equal to the sum of the second and third durations.

[0067] While performing steps 701 and 702, method 700 also includes performing step 705, which applies a second negative bias to the substrate holder. In one embodiment, step 705 is performed continuously during a first duration. Alternatively, step 705 may be performed during a fourth duration that begins after the first duration. In one embodiment, the fourth duration begins simultaneously with step 705 and is equal to the third duration.

[0068] Optionally, method 700 can be repeated by performing step 706, wherein step 706 repeats steps 701, 702, 703, 704, and 705. Optionally, step 706 can be repeated as needed to perform method 700 cyclically. In some embodiments, during the cyclical execution of method 700, one or more of the gases provided in step 701, the AC source power provided in step 702, or the second negative bias provided in step 705 (e.g., when continuously applied) can be modulated (e.g., pulsed) over a timescale substantially longer than the first duration.

[0069] FIG8 illustrates an exemplary method of plasma etching according to an embodiment of the present invention. The method of FIG8 can be performed by any of the plasma processing apparatus or plasma processing system described herein (e.g., plasma processing apparatus 100 of FIG1, plasma processing apparatus 200 of FIG2, or plasma processing apparatus 600 of FIG6). Furthermore, the schematic timing diagrams described herein (e.g., schematic timing diagram 300 of FIG3 or schematic timing diagram 500 of FIG5) may correspond to some or all of the portions of the method of FIG8. The method of FIG8 may be a specific embodiment of method 700 of FIG7.

[0070] Referring to FIG8, method 800 includes a step 801 of generating plasma in a processing chamber. In many embodiments, the plasma is ICP. After generating the inductively coupled plasma, the method includes a step 802 of forming a polymer layer on a first surface using an electron beam guided to a first surface of a substrate disposed in the processing chamber. The electron beam is generated at a second surface of an electron source electrode facing the first surface by a first negative bias during a first duration.

[0071] After the first duration, method 800 further includes step 803, which etches the polymer layer and the first surface of the substrate by accelerating the positive ions of the plasma toward the first surface using a second negative bias applied during the second duration.

[0072] Next, some or all of steps 801, 802, and 803 may be repeated. For example, after the initial plasma generation in step 801, plasma may be continuously generated while repeating optional step 804 (performing steps 802 and 803). In other words, method 800 includes repeatedly forming a polymer layer and subsequently etching the polymer layer and the substrate surface. Alternatively or additionally, plasma generation may be stopped at a certain point after performing step 803. In this case, optional step 805, returning to step 801, may be performed to cyclically execute method 800.

[0073] Exemplary embodiments of the present invention are summarized herein. Other embodiments may also be understood from the overall specification and the claims set forth herein.

[0074] Example 1: A plasma processing method includes cyclically performing the following steps: continuously supplying a gas to a processing chamber during a first duration; continuously supplying AC source power to a source power coupling element during the first duration while the gas is supplied, the AC source power generating plasma in the processing chamber; applying a first negative bias to an electron source electrode during a second duration while the gas and the AC source power are supplied, the first negative bias generating an electron beam guided to a substrate holder; removing the first negative bias from the electron source electrode during a third duration at the end of the second duration to stop the generation of the electron beam; applying a second negative bias to the substrate holder while the gas and the AC source power are supplied; and wherein the first duration is equal to the sum of the second duration and the third duration.

[0075] Example 2: The method of Example 1, wherein the step of applying the second negative bias includes: after the second duration, applying the second negative bias to the substrate holder during a fourth duration, the fourth duration being shorter than the first duration.

[0076] Example 3: The method of Example 2, wherein the fourth duration is equal to the third duration, and wherein the second negative bias is applied at the end of the second duration.

[0077] Example 4: The method of one of Examples 1 to 3, wherein the step of applying the second negative bias includes: continuously applying the second negative bias to the substrate holder during the first duration.

[0078] Example 5: The method of Example 4, wherein the second negative bias voltage is at a first value during the second duration, and the second negative bias voltage is at a second value different from the first value during the third duration.

[0079] Example 6: The method of one of Examples 1 to 5, wherein the second duration is shorter than about 3 ms.

[0080] Example 7: The method of one of Examples 1 to 6, wherein the first negative bias is a substantially constant DC voltage, and wherein the step of applying the second negative bias includes applying a radio frequency signal containing a negative DC offset to the substrate holder.

[0081] Example 8: A plasma etching method includes: generating an inductively coupled plasma in a processing chamber; forming a first polymer layer on the first surface using a first electron beam guided to a first surface of a substrate disposed in the processing chamber, the first electron beam being generated at a second surface of an electron source electrode facing the first surface by a first negative bias during a first duration; and after the first duration, accelerating positive ions of the inductively coupled plasma toward the first surface by using a second negative bias applied during a second duration to etch the first polymer layer and the first surface of the substrate.

[0082] Example 9: The method of Example 8 further includes: applying the second negative bias voltage during the first duration, the second negative bias voltage being less than the first negative bias voltage.

[0083] Example 10: The method of one of Examples 8 and 9, wherein the plasma etching method is ALE treatment.

[0084] Example 11: The method of one of Examples 8 to 10, wherein the plasma etching method is SAC etching.

[0085] Example 12: The method of one of Examples 8 to 11, wherein the first surface of the substrate is an exposed surface of a filling material disposed in a recessed region containing a high aspect ratio.

[0086] Example 13: The method is as in Example 12, where the aspect ratio is greater than approximately 50.

[0087] Example 14: The method of one of Examples 8 to 13 further includes: forming a second polymer layer on the third surface using a second electron beam directed to the third surface of the substrate, the second electron beam being generated on the second surface by a third negative bias during a third duration, wherein the third surface is an etched surface formed by etching the first polymer layer and the first surface; and after the third duration, accelerating the positive ions of the inductively coupled plasma toward the third surface by using a fourth negative bias applied during a fourth duration to etch the second polymer layer and the third surface of the substrate.

[0088] Example 15: A plasma processing apparatus includes: a processing chamber; a first DC power supply node; an electron source electrode coupled to the first DC power supply node and including a first surface, the electron source electrode being configured to generate a pulsed electron beam in the processing chamber using a first pulsed DC bias potential supplied to the electron source electrode by the first DC power supply node, wherein the first surface is located in the processing chamber; a substrate holder disposed in the processing chamber, the substrate holder including a second surface facing the first surface; and an RF source power coupling element disposed outside the processing chamber, the RF source power coupling element being configured to inductively couple RF source power to the plasma generated in the processing chamber.

[0089] Example 16: The plasma processing apparatus of Example 15, wherein the RF source power coupling element is an induction coil disposed around the processing chamber.

[0090] Example 17: A plasma processing apparatus such as one of Examples 15 and 16, wherein the RF source power coupling element is a spiral resonator.

[0091] Example 18: A plasma processing apparatus as in one of Examples 15 to 17, wherein the RF source power coupling element is an induction coil disposed above the processing chamber.

[0092] Example 19: A plasma processing apparatus as in one of Examples 15 to 18, wherein the substrate holder is coupled to a second DC power supply node, the second DC power supply node being configured to supply a second pulse DC bias potential.

[0093] Example 20: The plasma processing apparatus of one of Examples 15 to 19 further includes: an AC power supply node coupled to the electron source electrode, the electron source electrode being further configured to couple AC power to the plasma.

[0094] Although the invention has been described with reference to illustrative embodiments, this description should not be construed as limiting. Modifications and combinations of these illustrative embodiments and other embodiments of the invention will be apparent to those skilled in the art upon referring to these embodiments. Therefore, it is intended that any such modifications or embodiments be incorporated into the appended claims. 10: Processing Chamber 14: Electron Source Electrode 15: Emitter Surface 16: Substrate Holder 19: Surface 20: Plasma 21: Electron 22: Ballistic Electron 23: Captured Electron 24: Captured and Discharged Electron 25: Ion 27: Free Radical 29: Electron Beam 41: Beam Start-up Stage 42: Body Material 43: Mask 44: High Aspect Ratio Feature 45: Thin Conformal Layer 46: Filler Layer 47: Beam Shutdown Stage 48: Polymer Layer 49: Etching Depth 50: Ground 51: Ground 52: DC Bispension Generator Circuit 53: DC Bispension Supply Node 54: Source Power Generator Circuit 55: Source Power Supply Node 56: Bispension Power Generator Circuit 57: Bispension Power Supply Node 58: Optional AC Power Generator Circuit 59: Optional AC Power Supply Node 61: Vertical Dimension 63: Lateral Dimension 65: Outer Diameter 66: Inner Diameter 100: Plasma Processing Equipment 112: Source power coupling element; 140: Substrate; 200: Plasma processing equipment; 212: Source power coupling element; 331: Pulse period; 332: DC pulse; 333: DC pulse duration; 334: Source pulse; 335: Source pulse duration; 336: Bias pulse; 337: Bias pulse duration; 338: Gas pulse; 339: Gas pulse duration; 400: Plasma etching method; 440: Substrate; 531: Pulse period; 532: DC pulse; 533: DC pulse duration; 534: Source pulse; 535: Source pulse duration; 536: Bias pulse; 537: Bias pulse duration; 538: Gas pulse; 539: Gas pulse duration; 600: Plasma processing system; 700: Method; 701: Step; 702: Step; 703: Step; 704: Step; 705: Step; 706: Step; 800: Method; 801: Step; 802: Step; 803: Step; 804: Step; 805: Step [Simplified Explanation of the Diagram]

[0096] To more fully understand the present invention and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, wherein:

[0097] According to an embodiment of the present invention, FIG1 shows a schematic diagram of an exemplary plasma processing apparatus including an electronic source electrode and a source power coupling element;

[0098] According to an embodiment of the present invention, FIG2 shows a schematic diagram of another exemplary plasma processing apparatus including an electronic source electrode and a source power coupling element;

[0099] According to an embodiment of the present invention, FIG3 shows a schematic timing diagram of an exemplary method of plasma processing including DC pulses and bias pulses;

[0100] According to an embodiment of the present invention, FIG4 shows a schematic diagram of an exemplary method of plasma etching, the method comprising forming a polymer layer on a substrate using an electron beam and etching the polymer layer and the substrate;

[0101] According to an embodiment of the present invention, FIG5 shows a schematic timing diagram of another exemplary method of plasma processing including DC pulses and bias pulses;

[0102] According to an embodiment of the present invention, FIG6 shows a schematic diagram of an exemplary plasma processing system, which includes an electronic source electrode coupled to a DC bias supply node and a source power coupling element coupled to a source power supply node;

[0103] According to an embodiment of the present invention, FIG7 shows an exemplary method of plasma treatment;

[0104] According to an embodiment of the present invention, FIG8 shows an exemplary method of plasma etching;

[0105] Unless otherwise indicated, the corresponding numbers and symbols in the various figures generally refer to the corresponding components. These figures are drawn to clearly show the relevant features of the embodiments and are not necessarily drawn to scale. The edges of features drawn in these figures do not necessarily indicate the end of the feature's range.

Claims

1. A plasma processing method, comprising: continuously supplying a single gas to a processing chamber for a continuous duration without gas switching; generating an inductively coupled plasma in the processing chamber during the continuous duration; applying a first negative bias voltage at a first surface of an electron source electrode during the continuous duration, the first surface facing a second surface of a substrate disposed in the processing chamber, the first negative bias voltage generating a first electron beam comprising ballistic electrons directed to and impacting the second surface during the first duration, the first electron beam forming a first polymer layer at the second surface; removing the first negative bias voltage from the electron source electrode at the end of the first duration to stop the generation of the first electron beam during a second duration; and applying a second negative bias voltage to a substrate holder supporting the substrate during the second duration after the first duration and during the continuous duration, the second negative bias voltage etching the first polymer layer and the second surface of the substrate by accelerating positive ions of the inductively coupled plasma toward the second surface. The first negative bias voltage is a substantially constant DC voltage, and the step of applying the second negative bias voltage includes applying a radio frequency signal containing a negative DC offset to the substrate holder.

2. The plasma processing method of claim 1 further includes: applying the second negative bias voltage during the first duration, the second negative bias voltage being less than the first negative bias voltage.

3. The plasma processing method of claim 1, wherein the plasma processing method is atomic layer etching (ALE) processing.

4. The plasma processing method of claim 1, wherein the plasma processing method is a self-aligned contact window (SAC) etching process.

5. The plasma processing method of claim 1, wherein the second surface of the substrate is an exposed surface disposed in a recessed region containing a filling material with a high aspect ratio.

6. The plasma processing method of claim 5, wherein the aspect ratio is greater than about 50 and less than or equal to about 100.

7. The plasma processing method of claim 1 further comprises: forming a second polymer layer on the third surface using a second electron beam directed to the third surface of the substrate, the second electron beam being generated on the first surface by a third negative bias during a third duration, wherein the third surface is an etched surface formed by etching the first polymer layer and the second surface; and after the third duration, accelerating positive ions of the inductively coupled plasma toward the third surface by using a fourth negative bias applied during a fourth duration to etch the second polymer layer and the third surface of the substrate.

8. The plasma processing method of claim 1 further includes: applying the second negative bias to the substrate holder during the first duration.

9. The plasma processing method of claim 8, wherein the second negative bias voltage is at a first value during the first duration, and the second negative bias voltage is at a second value different from the first value during the second duration.

10. The plasma processing method of claim 1, wherein the step of applying the second negative bias includes continuously applying the second negative bias to the substrate holder during the continuous duration.

11. The plasma processing method of request item 1, wherein the first duration is less than about 3 ms.

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