Ion extraction optics with novel blocker configuration

Abstract

A processing system may include a plasma chamber and extraction optics disposed along a side of the plasma chamber. The extraction optics may include an extraction plate having an outer side and an inner side, wherein the extraction plate defines at least one extraction aperture. The extraction optics may include a beam blocker overlapping the at least one extraction aperture and disposed toward an inner side of the extraction plate. The beam blocker may have a cross-section defining a boomerang shape and may include a first metallic material, where the extraction plate includes a second metallic material. The processing system may also include a substrate platen disposed outside of the plasma chamber and movable relative to the extraction aperture along a scan direction.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of priority of U.S. Patent Application No. 18 / 080,555, filed on Dec. 13, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to plasma processing equipment, and more particularly, to ion - assisted processing and plasma - based ion sources. Background Art

[0004] Today, plasmas are used to process semiconductor substrates to fabricate integrated electronic circuits. In such applications, ions are involved in substrate etching, ion implantation, thin - film deposition, and other processes. Some processing equipment uses a plasma chamber that generates a plasma to act as an ion source for substrate processing. An ion beam can be extracted via extraction optics and directed to a substrate in a processing chamber located adjacent to the plasma chamber. Depending on how energy is transferred to the working gas, the plasma in the ion source can be generated in various ways such as rf excitation, dc, or microwave.

[0005] According to current designs, the ion extraction optics are formed using an extraction plate that includes an extraction aperture elongated along a given direction such that an elongated beam or ribbon beam is extracted from the plasma chamber. Particular extraction optics designs use ion - beam - shaping electrodes, or beam blockers, or simply a "blocker" located above the extraction slit. The blocker has the shape of a straight ruler, having a rectangular cross - section or a similar cross - section, and can extend longitudinally up to several hundred millimeters. Placing the beam blocker above the extraction aperture can create a pair of extraction slits formed along opposite edges of the extraction aperture. This configuration is suitable for generating a symmetric, angled ribbon beam that defines ion trajectories forming a non - zero angle of incidence with respect to the normal of the plane of the extraction plate. Thus, these angled ion beams will define a non - normal angle of incidence with respect to a substrate that can be placed in the vicinity of the extraction plate and parallel to the extraction plate.

[0006] Such an ion extraction device can be used for ion-assisted substrate etching. For example, providing ions at a non-normal angle of incidence can be used for various applications. By scanning the substrate at a constant speed in front of such an angled ribbon beam, the entire substrate can be exposed to the same ion treatment (ion energy, average angle, and ion dose). Known extraction devices employ a beam blocker and an extraction plate made of a dielectric material. This material is useful because, as compared to metallic materials that can contaminate the plasma with available metallic compounds, the dielectric material can resist degradation such as etching in a harsh chemical reaction plasma environment. In addition, for a given extraction optics geometry and the same operating parameters, it has been found that using a dielectric blocker and extraction plate results in a higher average beam angle as compared to an extraction optics using metallic beam blockers and extraction plates.

[0007] However, such dielectric materials can be relatively poor thermal conductors and can cause thermal gradients in the material, non-uniformity in temperature in the plasma chamber, drift in plasma chamber characteristics during processing of multiple substrates, and large variations in plasma chamber temperature as the processing conditions change. For example, these changes in plasma chamber temperature can be reflected in changes in the temperature of the process gas, resulting in unwanted variations in substrate etch rate.

[0008] In view of these and other considerations, the present disclosure is provided. SUMMARY OF THE INVENTION

[0009] In one embodiment, a processing system is provided that includes a plasma chamber and extraction optics disposed along one side of the plasma chamber. The extraction optics can include an extraction plate having an outer side and an inner side, where the extraction plate defines at least one extraction aperture. The extraction optics can include a beam blocker that overlaps the at least one extraction aperture and is disposed toward the inner side of the extraction plate. The beam blocker can have a cross-section that defines a boomerang shape and can include a first metallic material, where the extraction plate includes a second metallic material. The processing system can further include a substrate platen disposed outside the plasma chamber and movable relative to the extraction aperture along a scan direction.

[0010] In another embodiment, an extraction optics for an ion source is provided that includes an extraction plate having an outer side and an inner side, where the extraction plate defines at least one extraction aperture that extends along a first direction. The extraction optics can include a beam blocker that overlaps the at least one extraction aperture, is disposed toward the inner side of the extraction plate, and extends along the first direction, where the beam blocker and the at least one extraction aperture define a pair of extraction slits that extend along the first direction. The beam blocker can have a cross-section that defines a boomerang shape in a plane that is orthogonal to the first direction and can include a first metallic material, while the extraction plate includes a second metallic material.

[0011] In another embodiment, there is provided a beam blocker for an ion source, comprising: a beam blocker body extending along a first direction, wherein the beam blocker body has a cross-section defining a boomerang shape in a plane orthogonal to the first direction, and wherein the beam blocker body comprises a metallic material; and a dielectric film coating disposed over the surface of the beam blocker and encapsulating the beam blocker body. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A Shows an oblique view of an extraction optic according to an embodiment of the present disclosure.

[0013] Figure 1B Shows an oblique view of another extraction optic according to other embodiments of the present disclosure.

[0014] Figure 1C Shows an oblique view of yet another extraction optic according to an embodiment of the present disclosure.

[0015] Figure 1D Depicts an ion source according to an embodiment of the present disclosure.

[0016] Figure 1E Shows a close-up view of a portion of an extraction optic according to some embodiments of the present disclosure.

[0017] Figure 2A , Figure 2B and Figure 2C respectively show Figure 1A , Figure 1B , Figure 1C the modeling results of the embodiments of.

[0018] Figures 3A to 3E Shows a series of images depicting equipotential lines and the geometry of an ion beam configured for an extraction optic according to an embodiment of the present disclosure, wherein the Z-gap size varies between different figures.

[0019] Figure 4A Shows depicting by Figure 1B the ion angular distribution (function of beam current density versus average angle relative to the Z-axis) generated by the extraction optic depicted in.

[0020] Figure 4B Depicts the current density at the substrate as a function of the position along the Figure 1B substrate of the extraction optic.

[0021] Figure 5A Shows a graph depicting the average angle of an ion beam generated by an extraction optic of an embodiment of the present invention ( Figures 1A to 1C ), shown as a function of the Z-gap.

[0022] Figure 5B A comparison between a model depicting a variant of a beam blocker configured according to an embodiment of the present disclosure and experimental measurements of IAD.

[0023] Figures 6A to 6C Shows three different configurations of additional extraction optics according to a further embodiment of the present disclosure.

[0024] Figure 7A Depicts a side view of a processing device configured according to an embodiment of the present disclosure.

[0025] Figure 7B Depicts Figure 7A a top view of the processing device of

[0026] The figures are not necessarily to scale. The figures are for illustrative purposes only and are not intended to depict specific parameters of the present disclosure. The figures are intended to depict exemplary embodiments of the present disclosure and should not therefore be regarded as limiting the scope. In the figures, like reference numerals represent like elements. Detailed Description

[0027] The devices, systems, and methods according to the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which embodiments of the systems and methods are shown. The systems and methods may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The fact is that these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the systems and methods to those skilled in the art.

[0028] Terms such as "top", "bottom", "upper", "lower", "vertical", "horizontal", "lateral", and "longitudinal" may be used herein to describe the relative layout and orientation of these components and their parts with respect to the geometric structure and orientation of the components of the semiconductor manufacturing apparatus presented in the figures. The terms may include the specific words set forth, their derivatives, and words of similar meaning.

[0029] As used herein, an element or operation recited in the singular and preceded by the word group "a" or "an" is understood to potentially include a plurality of elements or operations. Additionally, reference to "one embodiment" of the present disclosure is not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features.

[0030] Devices for improving an ion source for generating an angled ion beam are provided herein.

[0031] Turning to the figures, Figure 1A An inclined view of an extraction assembly according to an embodiment of the present disclosure is shown, the extraction assembly being denoted as extraction optics 10. The extraction optics 10 may include an extraction plate 12 and a beam blocker 14. Also refer to Figure 1D, the extraction optical device 10 can be used in the ion source 100 to generate a pair of ion beams, which will be discussed below. The extraction plate 12 defines an extraction aperture 24, which can extend, for example, along the Figure 1D X direction as further shown in. The beam blocker 14 is disposed toward the inner side 12A of the extraction plate 12 and overlaps with the extraction aperture 24. Thus, the beam blocker 14 and the extraction aperture 24 define a pair of extraction slits, which are shown as the extraction slits 26 extending along the X direction.

[0032] The beam blocker 14 is characterized in that the beam blocker 14 defines a boomerang shape in cross section (meaning in the Y-Z plane), where the boomerang shape provides certain advantages for the extraction of ion beams, as will be further discussed below. Briefly, the boomerang shape defines a non-flat surface on the outer side 16 of the beam blocker 14. This shape presents two slightly flat surfaces with an obtuse angle between the two surfaces. In some non-limiting embodiments, the outer surface on the outer side 16 is inclined at an inclination of + / -12 degrees with respect to the vertical direction (Y-axis) of the drawing. The inner surface (facing the plasma side P) can be inclined at an inclination of + / -31 degrees with respect to the perpendicular to allow plasma diffusion. More generally, the boomerang shape according to other embodiments of the present disclosure may include two portions having an outer surface inclined at an inclination of + / -5 degrees to + / -30 degrees with respect to the Y-axis, where the Y-axis extends parallel to the main plane of the extraction plate 12. As will be described in detail below, by using a metal material as the beam blocker, this inclination with respect to the Y-axis will shape an electric field that tends to generate ion beams at a higher angle with respect to the Z-axis, which is used to achieve a higher incident angle of the ion beam with respect to the perpendicular to the main substrate plane (Z-axis), where such a higher angle is required for a given application.

[0033] Turning Figure 1B , which shows an inclined view of the extraction optical device 30 according to other embodiments of the present disclosure. The extraction optical device 30 may include the extraction plate 12 discussed above and the beam blocker 34. Also referring to Figure 1D , the extraction optical device 30 can be used in the ion source 100 to generate a pair of ion beams, which will be discussed below. The beam blocker 34 is also disposed toward the inner side 12A of the extraction plate 12 and overlaps with the extraction aperture 24. Thus, the beam blocker 34 and the extraction aperture 24 define a pair of extraction slits, which are shown as the extraction slits 46 extending along the X direction.

[0034] The beam blocker 34 is characterized in that the beam blocker 34 defines a circular boomerang shape in cross-section (meaning in the Y-Z plane), where the circular boomerang shape provides certain advantages for the extraction of the ion beam, as discussed further below. Briefly, the circular boomerang shape defines a non-flat, concave surface on the outer side 36 of the beam blocker 34. For example, the outer side 36 may have a bow shape defining a smaller portion of an arc, such as an arc of 20 degrees or 30 degrees. For example, in one non-limiting example, where the blocker 34 has a height of 35 mm along the Y-axis, the middle portion of the outer side may be a planar portion extending approximately 12 mm, and the adjacent portions at either end of the planar portion of the outer side 36 are curved portions, as Figure 2B further shown in. The inner side 38 of the beam blocker is also curved. Similar Figure 1A to the boomerang shape, by using a metallic material as the beam blocker, this concave surface (where the outer side of the distal end 34A of the circular boomerang structure is angled relative to the Y-axis (see Figure 2B )) will shape an electric field that also generates an ion beam at a higher angle relative to the Z-axis. Turning to the drawings, Figure 1C shows an inclined view of an extraction optical device 50 according to an embodiment of the present disclosure. The extraction optical device 50 may include an extraction plate 12, such as, and a beam blocker 54. Also referring to Figure 1D , the extraction optical device 10 may be used in an ion source 100 to generate a pair of ion beams, as discussed below. The beam blocker 54 is disposed toward the inner side 12A of the extraction plate 12 and overlaps with the extraction aperture 24. Thus, the beam blocker 54 and the extraction aperture 24 define a pair of extraction slits, which are shown as extraction slits 66 elongated along the X direction. In this embodiment, as well as the foregoing embodiments, the beam blocker 54 and the extraction plate 12 may be formed of a metallic material. In various embodiments of the present disclosure, the beam blocker may be composed of a first metallic material while the extraction plate is composed of a second metallic material, where the first metallic material may be the same as the second metallic material, while in other embodiments, the first metallic material may be the same as the second metallic material.

[0035] The beam blocker 54 is characterized in that the beam blocker 54 defines a flat surface on the outer side 56 in cross-section (meaning in the Y-Z plane). Specifically, the beam blocker 54 has a parallelepiped shape, where the inner corners are chamfered so as not to impede the plasma diffusion toward the extraction slit 66. In one embodiment, the beam blocker 54 may have a thickness of 5 mm to accommodate the cooling channel 18.

[0036] According to embodiments of the present disclosure, the beam blocker 14 and the extraction plate 12 may be made of a metallic material. In some embodiments, the beam blocker 14 includes a first metallic material, and the extraction plate 12 includes a second metallic material. In some cases, the beam blocker 14 and the extraction plate 12 may have the same material, such as aluminum. As Figure 1A depicted, the extraction plate 12 and the beam blocker 14 may have cooling channels, where the blocker cooling channel in the beam blocker 14 and the plate cooling channel in the extraction plate 12 are denoted as cooling channels 18. In some embodiments, the cooling channels 18 may be gun-drilled cooling channels, while in other embodiments, the cooling channels 18 may be welded cooling channels (formed by welding conduits on the bodies of the extraction plate 12 and the beam blocker 14).

[0037] Turning back again to Figure 1D , an ion source 100 is depicted, which includes a plasma chamber 102. One aspect of the design of the ion source 100 is to provide a structure for delivering wall temperature control, which can maintain the temperature of various parts of the ion source 100, the ion source 100 including the extraction plate 12, and beam blockers, such as beam blocker 14, beam blocker 34, or beam blocker 54. The internal volume 106 of the ion source 102 will contain a mixture of rarefied gas species during operation for generating plasma when energized by a power source (not shown). The ion source 100 may be inductively powered by rf power with a drive frequency between 400 kHz and 40 MHz. In an embodiment of the present invention as Figure 1D depicted, an internal antenna assembly may be used, where the antenna assembly is positioned inside the plasma chamber 102. Specifically, a linear antenna 112 coupled to a 13.56 MHz rf power source may be used to generate plasma inside the plasma chamber 102. A dielectric cylinder 114 is placed inside the plasma chamber 102. The dielectric cylinder 114 has a dual role: a) to seal the rarefied gas inside the plasma chamber 102 (i.e., act as a vacuum chamber wall) and ii) to allow the transmission of rf power from the rf antenna (linear antenna 112) to the rarefied gas inside the plasma chamber 102. The linear antenna 112 is positioned inside the dielectric cylinder 114 and may be formed by a hollow conduit to direct a cooling fluid therethrough. Additionally, atmospheric pressure gas may be blown out through the dielectric cylinder 114 to provide cooling to the outside of the linear antenna 112. The linear antenna may be surrounded by a cylindrical Faraday shield 116 concentrically aligned with the dielectric cylinder 114. The Faraday shield 114 has the effect of eliminating capacitive coupling and thus reducing sputtering of the dielectric cylinder 116.

[0038] As shown, cooling channels 18 are provided in the chamber wall, in the extraction plate 12, and in the beam blocker, and the channels extend parallel to the surface of the wall (meaning parallel to the X-axis). By running a coolant fluid whose temperature is controlled by a cooler, the temperature of the plasma chamber wall (see inner wall 105) and the extraction optics (extraction plate 12 and beam blocker (14, 34, 54)) can be controlled during operation. This increased temperature control can be reflected in smaller unwanted variations in the ion beam characteristics, resulting in better reproducibility of substrate etching or other substrate processing from wafer to wafer or over longer durations. To effectuate efficient heat transfer, the chamber body 103, the extraction plate 12, and the beam blocker can be made of a material having high thermal conductivity, such as a metal, and more specifically aluminum.

[0039] In various embodiments of the present disclosure, the extraction plate 12 can be integrally connected to the beam blocker, such as beam blocker 14, beam blocker 34, or beam blocker 54. Accordingly, the (one or more) cooling channels 18 in the beam blocker (14, 34, 54) can be communicatively coupled to the cooling channels 18 in the extraction plate 12, where coolant fluid from a single external source can flow through the beam blocker and the extraction plate of a given extraction assembly, such as extraction optics 10, extraction optics 30, or extraction optics 50. In other words, a given cooling channel of the extraction optics 10 can extend through the beam blocker and through the extraction plate 12. In addition to providing a convenient way to cool multiple portions of the extraction optics, this configuration also allows for the extraction optics to be conveniently removed and replaced as a single assembly as needed. In other embodiments, a beam blocker having a shape similar to beam blocker 14, beam blocker 34, or beam blocker 54 can be removably detachable from the extraction plate 12 and need not include a cooling channel. These other embodiments can be applicable to applications where cooling control of the beam blocker is not particularly needed.

[0040] In accordance with various embodiments of the present disclosure, the inner wall 105 of the plasma chamber 102, the extraction plate 12, and the blocker can be protected from the corrosive effects of these chemically reactive species. It should be noted that these components can be made of a metallic material in accordance with embodiments of the present invention and, without protection, would directly expose the metallic surface to the plasma formed in the plasma chamber 102. Particularly for an etch plasma, the molecular and atomic species generated inside the ion source 100 are typically highly reactive. If the metallic surface is not protected by the plasma, volatile metal compounds can form inside the ion source 100 and are then transported outside the plasma source to the surface of a substrate being processed outside the ion source 100 (i.e., in the processing chamber). For some of the volatile metal compounds, this situation can degrade or even destroy the semiconductor devices fabricated in the substrate.

[0041] Accordingly, in various embodiments of the present disclosure, the dielectric film coating 20 is disposed on the surfaces of the inner wall 105, the extraction plate 12, and the beam blockers (such as beam blocker 14, beam blocker 34, and beam blocker 54). An example of the dielectric film coating 20 of the extraction optical device 10 is shown in Figure 1E In this embodiment, an embodiment of the beam blocker 14 is shown, which has a beam blocker body 14A surrounded by the dielectric film coating 20. In other words, the dielectric film coating 20 is disposed on the entire surface of the beam blocker 14 in a manner that encapsulates the beam blocker body 14A.

[0042] In certain non-limiting embodiments, the thickness of the dielectric film coating 20 can be several tens of micrometers, one hundred micrometers, or several hundred micrometers. In one embodiment, the dielectric film coating 20 is formed of a mixture of Al2O3, Y2O3, and ZrO2. The mixture of these three refractory materials is highly resistant to the corrosive effects of highly reactive fluorocarbon, hydrocarbon, or chlorinated plasma species. The thickness of the dielectric film coating 20 (meaning a thickness of about several micrometers to several hundred micrometers) can be sufficient to prevent the beam blocker body 14A and the inner 12A and outer 12B sides of the extraction plate 12 from being exposed to the plasma, while being thin enough not to affect the distribution of the external electric field. In other words, when a voltage is applied between the extraction optical device 10, the extraction optical device 30, and the extraction optical device 50 and ground, the beam blocker 14 and the extraction plate 12 will behave as metal bodies (see Figures 2A to 2C , discussed below).

[0043] For example, the dielectric film coating 20 can be deposited by using a plasma spray gun. In some embodiments, once deposited, the dielectric film coating 20 can be polished to eliminate any defects, cracks, and / or pores, which, if not eliminated, can become centers of corrosion initiation during plasma processing. To facilitate post-deposition polishing, in accordance with embodiments of the present disclosure, the extraction plate 12 and a given beam blocker have a geometry with an open surface topology to allow deposition and subsequent polishing.

[0044] To facilitate efficient heat transfer, in various embodiments, the beam blocker and the extraction plate have a relatively low heat capacity, which means a small mass and a small volume. In one non-limiting example, in the exterior away from the extraction aperture 24, the extraction plate 12 has a plate thickness of 7 millimeters to allow a gun drill to form a cooling channel 18 with a 3-millimeter diameter.

[0045] According to various embodiments of the present disclosure, in the vicinity of the extraction aperture 24, the plate thickness is reduced to 3 millimeters. This reduction in the plate thickness near the extraction aperture 24 can help to promote a higher extraction beam current, as detailed in the following figures. Briefly, the extraction slit 26 has a relatively large plasma view field within the plasma chamber 102, meaning a larger solid angle allows for a larger ion diffusion area from the plasma and thus a larger number of ions extracted from the extraction aperture 24.

[0046] As mentioned above with respect to Figures 1A to 1C what has been mentioned, the shape of the beam blocker can vary according to different embodiments of the present disclosure. As detailed below, this shape will play a role in the characteristics of the ion beam extracted from the ion source 102, and in particular, in the ion angular distribution (IAD) and the range of the average angular value of the ion beam that can be generated by a given beam blocker shape.

[0047] Turning to Figure 2A 、 Figure 2B 、 Figure 2C which respectively show the results of OPERA modeling for the embodiments of Figure 1A 、 Figure 1B 、 Figure 1C . In these simulations, the plasma PL is generated on the left side of the figure when an extraction voltage of 1.7 kV magnitude is applied between the substrate 7 and the extraction optics including the beam blockers (14, 34, 54) and the extraction plate 12. To extract positive ions, the ion source and the extraction optics are kept at ground potential while the substrate is biased at a negative potential. The equipotential line distributions (in the conventional view, from 0 kV to -1.7 kV with a step of 100 V, and for the expanded view, from 0 V to -100 V with a step of 10 V) are shown to illustrate the qualitative shape of the generated electric field. As shown therein, the shape and direction of the ion beam are determined by the shape and orientation of the plasma meniscus that forms the boundary between the plasma and the vacuum. Via the laws of continuity and conservation of energy, the ion flux is related to the Bohm flux at the extraction aperture and thus to the total plasma density. Considering only singly ionized ions (Z = 1), the Bohm current density at the emission surface is given by

[0048]

[0049] where e represents the elementary charge, n0 represents the total ion density that should be equal to the electron density, kB represents the Boltzmann constant, Te represents the electron temperature, and mi represents the ion mass. In the model, the shape and position of the plasma meniscus are self-consistently solved by balancing the Bohm current density with the space-charge-limited current density given by the Child-Langmuir law

[0050]

[0051] where ε0 is the permittivity of vacuum, Ve is the extraction voltage, and z is the gap between the electrodes.

[0052] It should be noted that, according to embodiments of the present invention, and in Figures 2A to 2C the simulations of, the materials of the beam blockers (14, 34, 54) and the extraction plate 12 are metals and are thus good electrical conductors (due to the negligible dielectric film coating 20 with the lowest thickness). Since metals are opaque to electric field lines in Figures 2A to 2C the simulations of, the electrostatic field lines 208 cannot penetrate into the plasma as in the case of dielectric extraction optics used in known devices. On the outer surface (the surface facing the wafer or substrate side S), the electrostatic field lines follow the topology of the respective surface, except for the smaller portions of the extraction slits (26, 46, 66), where the electrostatic field lines protrude into the plasma PL more or less depending on the values of n0, Te, Ve, and z in the equilibrium equations discussed above. As depicted by comparing the Figures 2A to 2C field line shapes in, changing the profile of the beam blocker towards the substrate side S changes the distribution of the equipotential lines of the respective beam blockers in the regions adjacent to the extraction apertures 24 and the respective extraction slits (26, 46, 66), while the equipotential lines adjacent to the extraction plate 12 remain unchanged since the extraction plate 12 is the same in the three different embodiments. The meniscus 214 thus changes shape. For the vertical electrostatic field lines (meaning the field lines parallel to the Y-axis) in the region of the extraction aperture 24, as in the case of the Figure 2C embodiment of, the normal 216 on the meniscus surface in the center of the meniscus 214 has a specific inclination. For the Figure 2A case of the boomerang blocker depicted in, the field lines are inclined 12 degrees with respect to the vertical. This results in an increase in the inclination of the normal 216. For the Figure 2B circular boomerang depicted in, due to the circular outer side 36, the field lines are even more inclined with respect to the vertical (Z-axis). This geometry makes the normal 216 even more inclined. The inclination of the normal sets the initial direction of the extracted ion beams (209, 211, 215). A more inclined normal translates into a higher average angle of the extracted ion beams on the wafer (with respect to the vertical line (Z-axis) of the wafer plane (x-y plane)).

[0053] In various embodiments, an ion source 100 or a similar ion source can be used to generate angled ion beams in a compact ion beam processing apparatus that includes different configurations in which the extraction optics 10, the extraction optics 30, or the extraction optics 50 can be deployed to generate angled ion beams for substrate processing. Figure 7ADepict such a processing apparatus 700, where a plasma chamber 102 is disposed adjacent to a processing chamber 704. In Figure 7A the specific configuration shown, an extraction optic 10 is disposed on one side of the plasma chamber 102, where the extraction optic 10 is also adjacent to the processing chamber 704. When a plasma 712 is generated in the plasma chamber 102, an ion beam 710 can be extracted from the extraction optic 10. The ion beam 710 can be formed by two ion sub-beams that irradiate a substrate 708 at a symmetric non-zero angle with respect to a vertical line (meaning the Z-axis) of the main plane of the substrate 708 (meaning the X-Y plane in this example). Thus, by scanning the substrate holder 706 along the Y direction, the entire substrate 708 can be exposed to an angled ribbon ion beam that is elongated to cover the substrate 708 along the X-axis (see Figure 7B ). Additionally, as shown in Figure 7B , the substrate holder 706 can be movable along the Z direction to adjust the spacing (Z-gap) along the Z-axis between the substrate 708 and the extraction plate 12 and implicitly shape the ion angular distribution (IAD) without affecting the energy of the ions impinging on the substrate.

[0054] Turning to Figures 3A to 3E , which shows a series of images depicting the geometry of the equipotential lines (electrostatic field lines 208) of the extraction optic 30 described above and the ion beam 211, where the Z-gap varies between different figures. In Figure 3A the Z-gap is 6 mm; in Figure 3B the Z-gap is 10 mm; in Figure 3C the Z-gap is 14 mm; in Figure 3D the Z-gap is 18 mm; and in Figure 3E the Z-gap is 22 mm. Although Figures 3A to 3E shows the results for the extraction optic 30, the results for the extraction optic 10 and the extraction optic 50 are similar in nature. It should be noted that the plasma density, electron temperature, and extraction voltage are all the same in Figures 3A to 3E . It can be observed that although the plasma density, electron temperature, and extraction voltage are the same, the average angle of the ion beam 211 decreases as the length of the z-gap increases. In other words, the angle of the trajectory of the ion beam 211 becomes closer to the Z-axis direction as the Z-gap increases. This result can be a conclusion of the equilibrium equation discussed previously: as the z-gap increases, the electric field decreases, which is approximately equal to the extraction voltage divided by the z-gap length. The decrease in the electric field results in less penetration of the plasma, so the concave meniscus is smaller, then the normal 216 (for an explanation of the meniscus 214 and the normal 216 see Figure 2B ) has a smaller inclination with respect to the meniscus 214, and ultimately the average angle is smaller.

[0055] Figures 3A to 3E The qualitative observations in Figure 4A can be quantified. In Figure 4A the ion angular distribution (IAD) is shown as a graph that depicts the beam current density as a function of the average angle with respect to the Z-axis. The graph shows two distinct peaks (or sudden increases) in the beam density, which are symmetrically placed at approximately zero degrees (representing the Z-axis). The two distinct peaks represent the ion angular distribution (IAD) of the beam currents of two small beams that form the ion beam 211, as extracted using the extraction optics 30. The average angle of the IAD is measured with respect to the normal (Z-axis direction) on the substrate. As the Z-gap increases from 6 mm to 22 mm, the distribution of the current density for different cases indicates that the average angle decreases from 37 degrees to 20 degrees. Additionally, as Figure 4B depicted in Figure 4B the figure is a graph depicting the current density as a function of the position along the Y-axis, the on-wafer spacing of the small beams increases. Thus,

[0056] Turning to Figure 5A which shows a graph depicting the average angle of the ion beam produced by the extraction optics of an embodiment of the present invention, the graph is shown as a function of the Z-gap. Three different curves correspond to the geometries of the extraction optics 10, the extraction optics 30, and the extraction optics 50. As can be seen, the average angle decreases monotonically as the Z-gap increases. For the extraction optics 50, the average angle ranges between 17 degrees and 27 degrees. For the extraction optics 10, the average angle is shifted to higher angles, between 18 degrees and 32 degrees. For the extraction optics 30, the distribution is shifted to even higher angles, from 22 degrees to 37 degrees. Figure 5B A comparison between a model depicting a variant of the beam blocker 34 and experimental measurements of the IAD shows excellent agreement.

[0057] It should be noted that the average angle can also be varied by changing the extraction voltage of the ion beam. However, changing the extraction voltage also changes the ion energy of the ion beam, which completely shifts the characteristics of the etching process and, in the case of high energies, can even be harmful to the substrate to be processed. In the modeling results disclosed herein, the voltage used corresponds to the maximum extraction voltage used in plasma processing in actual applications. For lower extraction voltages, Figure 5A the curves in will shift downwards. It should also be noted that a suitable beam blocker can be selected based on specific application requirements. As a practical guideline, the beam blocker should provide an angular distribution having an average angle that belongs to the middle of the angular processing space.

[0058] Turning Figures 6A to 6C , which shows three different configurations of additional extraction optics according to another embodiment of the present disclosure. These embodiments are provided to address process throughput. To increase the etching rate of the substrate being processed, the overall extraction ion beam current must be increased. This increase in beam current can be achieved by increasing the number of extraction slits from 2 to 4, as shown in the extraction optics 600 of Figure 6A .

[0059] In this example, the side cross-sectional view shows an extraction plate 602 having two extraction apertures shown as extraction apertures 614. A boomerang-shaped beam blocker shown as beam blocker 604 is disposed adjacent to each extraction aperture, which defines four extraction slits shown as extraction slits 616. As shown, cooling channels 608 are also provided, which can be fabricated by gun drilling (a complex machining process for long channel fabrication), and the channels can extend to about 400 mm. More generally, according to an embodiment of the present disclosure, the extraction optics can include a plurality of n extraction apertures, and a plurality of n beam blockers are disposed to respectively overlap the plurality of n extraction apertures, where n represents any suitable integer greater than 1.

[0060] Turning Figure 6B and Figure 6C , which shows an alternative configuration of a six-slit extraction optic. In Figure 6B , the extraction optics 620 includes an extraction plate 622 having three extraction apertures shown as extraction apertures 634. A curved boomerang-shaped beam blocker shown as beam blocker 624 is disposed adjacent to each extraction aperture and overlaps the aperture, which defines six extraction slits shown as extraction slits 636. As shown, cooling channels 628 are also provided, which can be fabricated by gun drilling.

[0061] Turning Figure 6C , the extraction optics 640 includes an extraction plate 642 having three extraction apertures shown as extraction apertures 654. A curved boomerang-shaped beam blocker shown as beam blocker 644 is disposed adjacent to each extraction aperture, which defines six extraction slits shown as extraction slits 656. As shown, cooling channels 648 are also provided, which can be fabricated by welding smaller U-shaped structures to the bodies of the beam blocker 644 and the extraction plate 642 as shown. This method can be particularly useful for the fabrication of extremely wide extraction optics, where the beam blocker and the extraction plate can be elongated to dimensions of 300 mm, 400 mm, or greater than 400 mm, where gun drilling can prove more difficult or time-consuming for fabricating such long channels.

[0062] In view of the foregoing, the present disclosure provides at least the following advantages: i) The novel extraction equipment disclosed herein allows controlling the plasma chamber temperature and implicitly controlling the gas temperature; thus, the etching rate variation and process drift between wafers can be reduced or eliminated; ii) The extraction ion beam can have an IAD characterized by an average angle similar to that of a dielectric optical device; iii) The extraction beam current and the implicit process yield can be increased by increasing the number of slits without affecting the chamber temperature control.

[0063] Although certain embodiments of the present disclosure have been described herein, the present disclosure is not limited thereto, since the scope of the present disclosure is as broad as the scope permitted by the art and the present specification may be read in a similar manner. Therefore, the above description should not be construed as restrictive. Such modifications within the scope and spirit of the claims will be envisioned by those skilled in the art.

Claims

1. A processing system, comprising: A plasma chamber; An extraction optical device disposed along one side of the plasma chamber, comprising: An extraction plate having an outer side and an inner side, the extraction plate defining at least one extraction aperture; A beam blocker overlapping with the at least one extraction aperture and disposed toward the inner side of the extraction plate, Wherein the beam blocker has a cross-section defining a boomerang shape, and Wherein the beam blocker comprises a first metal material and the extraction plate comprises a second metal material; and A substrate stage disposed outside the plasma chamber and movable relative to the at least one extraction aperture along a scanning direction.

2. The processing system according to claim 1, wherein the beam blocker comprises at least one blocker cooling channel, and wherein the extraction plate comprises at least one plate cooling channel.

3. The processing system according to claim 2, wherein the at least one blocker cooling channel comprises a gun-drilled cooling channel and the at least one plate cooling channel comprises a gun-drilled cooling channel.

4. The processing system according to claim 2, wherein the at least one blocker cooling channel comprises a welded cooling channel and the at least one plate cooling channel comprises a welded cooling channel.

5. The processing system according to claim 1, wherein the boomerang shape is a circular boomerang shape.

6. The processing system according to claim 1, wherein the at least one extraction aperture comprises a plurality of n extraction apertures, and wherein a plurality of n beam blockers are disposed to overlap with the plurality of n extraction apertures respectively.

7. The processing system according to claim 1, the beam blocker and the at least one extraction aperture extend along a first direction and define a pair of extraction slits extending along the first direction.

8. The processing system according to claim 1, wherein the first metal material and the second metal material are aluminum.

9. An extraction optical device for an ion source, comprising: An extraction plate having an outer side and an inner side, the extraction plate defining at least one extraction aperture extending along a first direction; And A beam blocker overlapping with the at least one extraction aperture, disposed toward the inner side of the extraction plate and extending along the first direction, the beam blocker and the at least one extraction aperture defining a pair of extraction slits extending along the first direction, Wherein the beam blocker has a cross-section defining a boomerang shape in a plane orthogonal to the first direction, and Wherein the beam blocker comprises a first metal material and the extraction plate comprises a second metal material.

10. The extraction optical device according to claim 9, wherein the first metal material and the second metal material comprise aluminum.

11. The extraction optical device according to claim 9, wherein the at least one extraction aperture and the beam blocker extend along a first direction, wherein the beam blocker comprises at least one blocker cooling channel, and wherein the extraction plate comprises at least one plate cooling channel.

12. The extraction optical device according to claim 9, wherein the boomerang shape includes a circular boomerang shape.

13. The extraction optical device according to claim 9, wherein the at least one extraction aperture includes a plurality of n extraction apertures, and wherein a plurality of n beam blockers are arranged to respectively overlap with the plurality of n extraction apertures.

14. The extraction optical device according to claim 11, wherein the extraction plate is integrally connected to the beam blocker, and wherein the at least one blocker cooling channel is communicatively coupled to the at least one plate cooling channel.

15. A beam blocker for use in an ion source, comprising: a beam blocker body extending along a first direction, wherein the beam blocker body has a cross-section defining a boomerang shape in a plane orthogonal to the first direction, and wherein the beam blocker body includes a metallic material; and a dielectric film coating disposed over a surface of the beam blocker and encapsulating the beam blocker body.

16. The beam blocker according to claim 15, wherein the boomerang shape includes a circular boomerang shape.

17. The beam blocker according to claim 16, wherein an outer side of the beam blocker includes a planar portion and a pair of curved portions adjacent to the planar portion.

18. The beam blocker according to claim 17, wherein an inner side of the beam blocker is curved.

19. The beam blocker according to claim 15, wherein the metallic material includes aluminum.

20. The beam blocker according to claim 15, wherein the beam blocker includes at least one blocker cooling channel extending along the first direction.

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