Ion extraction optics with a novel blocker configuration.

Abstract

The 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 and defining at least one extraction aperture. The extraction optics may include a beam blocker overlapping the at least one extraction aperture and disposed toward the 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, and the extraction plate may include a second metallic material. The processing system may further include a substrate platen disposed outside the plasma chamber and movable along a scanning direction relative to the extraction aperture.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. patent application Ser. No. 18 / 080,555, filed Dec. 13, 2022, the entire contents of which are incorporated herein by reference.

[0002] Field of the Disclosure

[0002] The present disclosure relates generally to plasma processing equipment, and more particularly to ion-assisted processing and plasma-based ion sources. [Background technology]

[0003]

[0003] Plasmas are currently used in the processing of semiconductor substrates to create integrated electronic circuits. These applications involve ions in substrate etching, ion implantation, thin film deposition, and other processes. Some processing equipment employs a plasma chamber to generate a plasma that serves as an ion source for substrate processing. An ion beam is extracted through extraction optics and directed toward the substrate in a processing chamber located adjacent to the plasma chamber. Depending on the method of energy delivery to the working gas, plasma can be generated in the ion source in a variety of ways, including RF excitation, direct current, and microwaves.

[0004]

[0004] In recent designs, ion extraction optics are formed using an extraction plate containing an elongated extraction aperture along a predetermined direction so that an elongated or ribbon beam is extracted from the plasma chamber. Certain extraction optics designs employ ion beam shaping electrodes, or beam blockers, or simply "blockers," positioned over the extraction slit. The blockers have a ruler shape, a rectangular cross section, or a similar cross section, and can extend up to several hundred millimeters in the longitudinal direction. By placing the beam blockers over the extraction aperture, a pair of extraction slits can be formed along opposite edges of the extraction aperture. This configuration is suitable for generating symmetrically angled ribbon beams that define ion trajectories that form non-zero angles of incidence with respect to a normal to the plane of the extraction plate. These angled ion beams therefore define a non-normal angle of incidence with respect to a substrate positioned near the extraction plate, which may be parallel to the extraction plate.

[0005] Such ion extraction devices can be used, for example, in ion-assisted substrate etching, where delivering ions at a non-normal incidence angle can be useful for a variety of applications. By scanning a substrate at a constant velocity 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 beam blockers and extraction plates made of dielectric materials. Dielectric materials are useful because they can withstand degradation, such as etching, in harsh, chemically reactive plasma environments, as opposed to metallic materials that can contaminate the plasma with metal compounds. Furthermore, the use of dielectric blockers and extraction plates has been shown to provide a higher average beam angle for a given extraction optic geometry and identical operating parameters, compared to extraction optics using metallic beam blockers and extraction plates.

[0006] However, such dielectric materials are relatively poor conductors of heat, which can lead to thermal gradients within the material, temperature non-uniformities within the plasma chamber, drift in plasma chamber characteristics during processing of multiple substrates, and larger changes in plasma chamber temperature with changing process conditions. Such changes in plasma chamber temperature can be reflected in changes in process gas temperatures, resulting in, for example, undesirable variations in substrate etch rates.

[0007]

[0007] It is with respect to these and other considerations that the present disclosure is provided. Summary of the Invention

[0008] In one embodiment, a processing system is provided that includes a plasma chamber and extraction optics disposed along a side of the plasma chamber. The extraction optics can include an extraction plate having an outer side and an inner side and defining at least one extraction aperture. The extraction optics can include a beam blocker overlapping the at least one extraction aperture and disposed toward the inner side of the extraction plate. The beam blocker can have a cross section defining a boomerang shape and can include a first metallic material, and the extraction plate can include a second metallic material. The processing system can further include a substrate platen disposed outside the plasma chamber and movable along a scanning direction relative to the extraction aperture.

[0009] In another embodiment, extraction optics for an ion source are provided, the extraction optics including an extraction plate having an outer side and an inner side and defining at least one extraction aperture elongated along a first direction. The extraction optics can include a beam blocker overlapping the at least one extraction aperture and disposed along the first direction toward the inside of the extraction plate. The beam blocker and the at least one extraction aperture define a pair of extraction slits elongated along the first direction. The beam blocker can have a cross section defining a boomerang shape in a plane perpendicular to the first direction and can include a first metallic material, and the extraction plate includes a second metallic material.

[0010]

[0010] In a further embodiment, a beam blocker for use in an ion source is provided, comprising: a beam blocker body elongated along a first direction, having a cross-section defining a boomerang shape in a plane perpendicular to the first direction, the beam blocker body comprising a metal material; and a dielectric film coating disposed on a surface of the beam blocker and encapsulating the beam blocker body. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1A is an oblique view of extraction optics according to an embodiment of the present disclosure; FIG. 1B is an oblique view of another extraction optics according to another embodiment of the present disclosure; FIG. 1C is an oblique view of further extraction optics according to an embodiment of the present disclosure; FIG. 1D is a diagram of an ion source according to an embodiment of the present disclosure; and FIG. 1E is a close-up view of a portion of extraction optics according to some embodiments of the present disclosure. [Figure 2] 1A, 1B, and 1C show modeling results for the embodiments of FIGS. 1A, 1B, and 1C, respectively. [Figure 3] 1A-E show a series of images depicting the equipotential lines and ion beam geometry of extraction optics arranged in accordance with an embodiment of the present disclosure, with varying Z-gap dimensions between the different images. [Figure 4] FIG. 1B shows the ion angular distribution (beam current density as a function of average angle relative to the Z-axis) produced by the extraction optics shown in FIG. 1B, and FIG. 1B shows the current density at the substrate of the extraction optics of FIG. 1B as a function of position along the substrate. [Figure 5] FIG. 1A is a graph showing the average angle of the ion beam generated by the extraction optics (FIGS. 1A-1C) of the present embodiment as a function of Z-gap, and FIG. 1B is a comparison of modeled and experimentally measured IAD for variations of the beam blocker positioned in accordance with an embodiment of the present disclosure. [Figure 6] 1A-C show three different configurations of additional extraction optics according to further embodiments of the present disclosure. [Figure 7] 7A is a side view of a processing device arranged in accordance with an embodiment of the present disclosure, and FIG. 7B is a top view of the processing device of FIG. 7A. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0025] The drawings are not necessarily to scale. The drawings are merely representational and are not intended to depict specific parameters of the present disclosure. The drawings are intended to depict exemplary embodiments of the present disclosure and therefore should not be considered limiting in scope. In the drawings, like numbering represents like elements.

[0013]

[0026] The apparatus, systems, and methods according to the present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the systems and methods are shown. The present systems and methods may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, 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.

[0014]

[0027] Terms such as "top," "bottom," "upper," "lower," "vertical," "horizontal," "lateral," and "longitudinal" may be used herein to describe the relative placement and orientation of semiconductor manufacturing equipment components and their constituent parts with respect to their geometries and orientations as shown in the figures. The terms may include specifically mentioned words, derivatives thereof, and similar phrases.

[0015]

[0028] As used herein, elements or steps described in the singular and preceded by the word "a" or "an" should be understood to also include a plurality of elements or steps. Furthermore, references to "one embodiment" of the present disclosure should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0016]

[0029] Provided herein is an apparatus for improving an ion source used to generate an angled ion beam.

[0017]

[0030] Reference is made to FIG. 1A , which illustrates an oblique view of an extraction assembly, designated extraction optic 10, according to an embodiment of the present disclosure. Extraction optic 10 can include an extraction plate 12 and a beam blocker 14. Referring also to FIG. 1D , extraction optic 10 can be used in an ion source 100 to generate a pair of ion beams, as described below. Extraction plate 12 defines an extraction aperture 24, which may be elongated along, for example, the X direction, as further illustrated in FIG. 1D . Beam blocker 14 is positioned toward the interior 12A of extraction plate 12 so as to overlap extraction aperture 24. In this manner, beam blocker 14 and extraction aperture 24 define a pair of extraction slits, shown as elongated extraction slits 26, along the X direction.

[0018]

[0031] A feature of the beam blocker 14 is that it defines a boomerang shape in cross section, meaning in the YZ plane, which provides certain advantages for ion beam extraction, as explained further below. Briefly, the boomerang shape defines a non-planar surface on the exterior 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 of the exterior 16 is inclined at ±12 degrees relative to the vertical direction (Y axis) of the figure. The inner surface (facing the plasma side P) may be inclined at ±31 degrees relative to the normal to enable plasma diffusion. More generally, a boomerang shape according to other embodiments of the present disclosure may include two sections with outer surfaces inclined at ±5 degrees to ±30 degrees relative to the Y axis, which extends parallel to the major plane of the extraction plate 12. As will be described in more detail below, by using a metallic material as a beam blocker, this tilt relative to the Y-axis creates an electric field that tends to produce an ion beam at a higher angle relative to the Z-axis, which is useful for achieving a high ion beam incidence angle relative to the normal to the main substrate surface (Z-axis) when such a high angle is desired by a given application.

[0019]

[0032] 1B, which is an oblique view illustrating extraction optics 30 according to another embodiment of the present disclosure. Extraction optics 30 can include the extraction plate 12 described above and a beam blocker 34. Referring also to FIG. 1D, extraction optics 30 can be used in an ion source 100 to generate a pair of ion beams, described below. The beam blocker 34 is also positioned toward the inner side 12A of the extraction plate 12 so as to overlap the extraction aperture 24. In this manner, the beam blocker 34 and the extraction aperture 24 define a pair of extraction slits, shown as elongated extraction slits 46 along the X direction.

[0020]

[0033] A feature of the beam blocker 34 is that it defines a rounded boomerang shape in a cross section taken in the YZ plane, which provides particular advantages for ion beam extraction, as described further below. Briefly, the rounded boomerang shape defines a non-planar concave surface on the outer side 36 of the beam blocker 34. For example, the outer side 36 may have an arcuate shape defining a small arcuate portion, e.g., a 20-degree or 30-degree arc. In one non-limiting example, if the blocker 34 has a height of 35 mm along the Y axis, the central portion of the outer side may be flat extending approximately 12 mm, and the adjacent portions of the flat portion of the outer side 36 at both ends are curved, as further shown in FIG. 2B . The inner side 38 of the beam blocker is also curved. By using a metal material as a beam blocker, as in the boomerang shape of FIG. 1A , the concave outer surface of the distal end 34A of the rounded boomerang structure, angled relative to the Y-axis (see FIG. 2B ), creates an electric field that generates an ion beam at a higher angle relative to the Z-axis. See FIG. 1C , which is a perspective view of an extraction optic 50 according to an embodiment of the present disclosure. The extraction optic 50 can include an extraction plate 12 and a beam blocker 54. Also see FIG. 1D , the extraction optic 10 can be used in an ion source 100 to generate a pair of ion beams, as described below. The beam blocker 54 is positioned toward the inner side 12A of the extraction plate 12 so as to overlap the extraction aperture 24. The beam blocker 54 and the extraction aperture 24 thus define a pair of elongated extraction slits, shown as extraction slits 66, along the X-direction. As in the previous embodiment, the beam blocker 54 and extraction plate 12 in this embodiment can be formed of a metal material. In various embodiments of the present disclosure, the beam blocker may be made of a first metallic material and the extraction plate may be made of a second metallic material, and the first metallic material may be the same as the second metallic material, and in other embodiments, the first metallic material may be the same as the second metallic material.

[0021]

[0034] A feature of the beam blocker 54 is that the beam blocker 54 defines a plane on the exterior 56 in a cross section meaning in the YZ plane. In particular, the beam blocker 54 has a parallelepiped shape with chamfered interior corners so as not to impede plasma diffusion towards the extraction slit 66. In one embodiment, the beam blocker 54 may be provided with a thickness of 5 mm to accommodate the cooling channels 18.

[0022]

[0035] According to embodiments of the present disclosure, the beam blocker 14 and the extraction plate 12 may be made of metallic materials. 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 be the same material, such as aluminum. As shown in FIG. 1A , the extraction plate 12 and the beam blocker 14 may include cooling channels, and the blocker cooling channels of the beam blocker 14 and the plate cooling channels of the extraction plate 12 are referred to as cooling channels 18. In some embodiments, the cooling channels 18 may be gun-drilled cooling channels, and in other embodiments, the cooling channels 18 may be welded cooling channels (made of welded tubing on the bodies of the extraction plate 12 and the beam blocker 14).

[0023]

[0036] Reference is again made to FIG. 1D , which illustrates an ion source 100 including a plasma chamber 102. One aspect of the design of the ion source 100 is the provision of a structure for providing wall temperature control that can maintain the temperature of various portions of the ion source 100, including the extraction plate 12, as well as a beam blocker, such as beam blocker 14, beam blocker 34, or beam blocker 54. The interior region 106 of the ion source 102 contains a dilute mixture of gaseous species that, when energized by a power supply (not shown), generates a plasma. The ion source 100 can be inductively powered by RF power at a drive frequency between 400 kHz and 40 MHz. As shown in FIG. 1D , in this embodiment, an internal antenna assembly can be used, and the antenna assembly is located within the plasma chamber 102. Specifically, a linear antenna 112 coupled to a 13.56 MHz RF power source can be used to generate plasma within the plasma chamber 102. A dielectric cylinder 114 is disposed within the plasma chamber 102. The dielectric cylinder 114 has the dual role of a) sealing the rarefied gas inside the plasma chamber 102 (i.e., functioning as a vacuum chamber wall) and ii) enabling 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 located inside the dielectric cylinder 114 and is formed as a hollow tube through which a cooling fluid can pass. Additionally, atmospheric pressure gas can be blown through the interior of the dielectric cylinder 114 to cool the exterior of the linear antenna 112. The linear antenna may be surrounded by a cylindrical Faraday shield 116 aligned concentrically with the dielectric cylinder 114. The Faraday shield 114 serves to reduce sputtering of the dielectric cylinder 116 by eliminating capacitive coupling.

[0024]

[0037] As shown, the chamber walls, extraction plate 12, and beam blocker are provided with cooling channels 18 running parallel to the wall surfaces, i.e., parallel to the X-axis. By flowing a cooling fluid whose temperature is controlled by the cooling device, the temperature of the plasma chamber walls (see inner wall 105) and extraction optics (extraction plate 12 and beam blockers (14, 34, 54)) can be controlled during processing. This improved temperature control can be reflected in a reduction in unwanted variations in ion beam characteristics, leading to improved reproducibility of substrate etching or other substrate processing from wafer to wafer or over longer periods of time. For efficient heat transfer, the chamber body 103, extraction plate 12, and beam blocker can be made of a material with high thermal conductivity, such as metal, more specifically, aluminum.

[0025]

[0038] In various embodiments of the present disclosure, the extraction plate 12 may be integrally connected to a beam blocker, such as beam blocker 14, beam blocker 34, or beam blocker 54. In this manner, the cooling channels 18 of the beam blocker (14, 34, 54) may be fluidly coupled to the cooling channels 18 of the extraction plate 12, allowing cooling fluid from a single external source to flow through the beam blocker and extraction plate of a given extraction assembly, such as extraction optic 10, extraction optic 30, or extraction optic 50. In other words, the cooling channels of a given extraction optic 10 may run through the beam blocker and through the extraction plate 12. This configuration not only provides a convenient approach to cooling multiple portions of the extraction optic, but also allows the extraction optic to be conveniently removed and replaced as a single component as needed. In other embodiments, beam blockers similar in shape to beam blocker 14, beam blocker 34, or beam blocker 54 may be separately removable from the extraction plate 12 and need not include cooling channels. Such other embodiments may be particularly suitable for applications where controlled cooling of the beam blocker is not required.

[0026]

[0039] According to various embodiments of the present disclosure, the inner walls 105, extraction plate 12, and blockers of the plasma chamber 102 can be protected from the corrosive effects of these chemically reactive species. It should be noted that these components may be made of metallic materials according to the present embodiments, and if unprotected, would result in direct exposure of the metal surfaces to the plasma formed in the plasma chamber 102. The molecular and atomic species generated within the ion source 100, particularly for etching plasmas, are typically highly reactive. If the metal surfaces are not protected from the plasma, volatile metal compounds can form within the ion source 100 and be transported outside the plasma source, i.e., to the surface of a substrate being processed in the processing chamber. Some volatile metal compounds can degrade or even destroy semiconductor devices being fabricated in the substrate.

[0027]

[0040] Therefore, according to various embodiments of the present disclosure, a dielectric film coating 20 is provided 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 is shown in FIG. 1E for the extraction optic 10. In this example, an embodiment of the beam blocker 14 is shown having a beam blocker body 14A surrounded by the dielectric film coating 20. In other words, the dielectric film coating 20 is disposed over the entire surface of the beam blocker 14 so as to encapsulate the beam blocker body 14A.

[0028]

[0041] In certain non-limiting embodiments, the thickness of the dielectric film coating 20 can be tens of micrometers, hundreds of micrometers, or hundreds of micrometers. In one embodiment, the dielectric film coating 20 is formed from a mixture of Al2O3, YO3, and ZrO2. This mixture of three refractory materials is highly resistant to the corrosive effects of reactive fluorocarbon, hydrocarbon, or chlorinated plasma species. The thickness of the dielectric film coating 20, i.e., on the order of several micrometers to several hundred micrometers, can be sufficient to prevent the inner and outer surfaces 12A and 12B of the beam blocker body 14A and 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 optics 10, 30, and 50 and ground, the beam blocker 14 and extraction plate 12 function as metallic bodies (see FIGS. 2A-2C, described below).

[0029]

[0042] The dielectric film coating 20 may be deposited, for example, by using a plasma spray gun. In some embodiments, the dielectric film coating 20 may be polished after deposition to remove any defects, cracks, and / or pores that, if not removed, may become erosion initiation centers during plasma processing. To facilitate polishing after deposition, according to embodiments of the present disclosure, the extraction plate 12 and certain beam blockers have geometries with open-face topologies that allow for deposition and subsequent polishing.

[0030]

[0043] To promote efficient heat transfer, in various embodiments, the beam blocker and extraction plate have a relatively low thermal mass, which means a small mass and a small volume. In one non-limiting example, the extraction plate 12 has a plate thickness of 7 mm in the outer portion away from the extraction apertures 24 to allow for gun drilling of 3 mm diameter cooling channels that form the cooling channels 18.

[0031]

[0044] According to various embodiments of the present disclosure, the plate thickness near the extraction aperture 24 is reduced to 3 mm. This reduction in plate thickness near the extraction aperture 24 may help facilitate higher extracted beam currents, as will be described in more detail in the following figures. In essence, the extraction slit 26 has a relatively larger field of view of the plasma in the plasma chamber 102, i.e., a larger solid angle, allowing for a larger ion diffusion area from the plasma, and therefore, allowing for more ions to be extracted from the extraction aperture 24.

[0032]

[0045] 1A-1C, the shape of the beam blocker can vary according to different embodiments of the present disclosure. As described in more detail below, this shape plays a role in the characteristics of the ion beam extracted from the ion source 102, particularly the ion angular distribution (IAD) and range of mean angular values ​​of the ion beam that can be produced by a given beam blocker shape.

[0033]

[0046] See Figures 2A, 2B, and 2C, which show the results of OPERA modeling for the embodiments of Figures 1A, 1B, and 1C, respectively. In these simulations, a plasma PL is generated on the left side of the figure, and an extraction voltage having a magnitude of 1.7 kV is applied between the substrate 7 and the extraction optics, which include the beam blockers (14, 34, and 54) and extraction plate 12. To extract positive ions, the ion source and extraction optics are held at ground potential, and the substrate is biased to a negative potential. Equipotential distributions are shown (0 to -1.7 kV in 100 V steps in the normal view and 0 to -100 V in 10 V steps in the enlarged view) to illustrate the qualitative shape of the resulting electric field. As shown in the figures, the shape and direction of the ion beam are determined by the shape and orientation of the plasma meniscus, which forms the boundary between the plasma and vacuum. By the law of continuity and the law of conservation of energy, the ion flux is related to the Bohm flux at the extraction aperture, and thereby to the bulk plasma density. Considering only a single ion (Z=1), the Bohm current density at the emitting surface is given by: TIFF2025539538000002.tif14170

[0034]

[0047] In the above equation, e is the elementary charge, n0 is the ion bulk density, which is assumed to be equal to the electron density, and k B is the Boltzmann constant, T e is the electron temperature, m i denotes the ion mass. In this model, the shape and position of the plasma meniscus are solved self-consistently by balancing the Bohm current density against the space-charge-limited current density given by the Child-Langmuir law. JPEG2025539538000003.jpg29170In the above formula, ε0 is the dielectric constant of a vacuum, V e is the extraction voltage and z is the interelectrode gap.

[0035]

[0048] Note that in the simulations of Figures 2A-2C, according to this embodiment, the material of the beam blocker (14, 34, 54) and extraction plate 12 is metal and therefore a good electrical conductor (the dielectric film coating 20 can be neglected due to its minimal thickness). In the simulations of Figures 2A-2C, metal is opaque to the electric field lines, so the electrostatic field lines 208 cannot penetrate into the plasma, as is the case with dielectric extraction optics used in known devices. At the outer surface (facing the wafer, or substrate side S), the electrostatic field lines are expressed as n0, T in the balance equations given above. e , V e, and a small portion of the extraction slits (26, 46, 66), where the electrostatic field lines protrude somewhat into the plasma PL depending on the value of z. As shown by comparing the electric field line shapes in Figures 2A-2C, changing the shape of the outer side of the beam blocker toward the substrate side S changes the distribution of equipotential lines adjacent to each beam blocker in the region of the extraction aperture 24 and each extraction slit (26, 46, 66), while the equipotential lines adjacent to the extraction plate 12 remain unchanged because the extraction plate 12 is the same in the three different embodiments. The meniscus 214 then changes shape accordingly. For vertical electrostatic field lines in the region of the extraction aperture 24, i.e., electric field lines parallel to the Y-axis, as in the embodiment of Figure 2C, the normal 216 to the meniscus surface at the center of the meniscus 214 has a constant inclination. In the case of the boomerang blocker shown in Figure 2A, the electric field lines are inclined by 12 degrees relative to the vertical, resulting in a larger inclination of the normal 216. In the case of the rounded boomerang shown in Figure 2B, the electric field lines are more tilted relative to the normal (Z-axis) due to the rounded outer side 36. This geometry causes the normal 216 to be more tilted. The tilt of the normal sets the initial direction of the extracted ion beam (209, 211, 215). The more tilted the normal, the higher the average angle on the wafer (relative to the normal (Z-axis) to the wafer plane (xy-plane)) of the extracted ion beam.

[0036]

[0049] In various embodiments, an angled ion beam may be generated using ion source 100 or a similar ion source in a compact ion beam processing apparatus, including different configurations in which extraction optics 10, extraction optics 30, or extraction optics 50 may be arranged to generate an angled ion beam for substrate processing. FIG. 7A illustrates such a processing apparatus 700, in which a plasma chamber 102 is positioned adjacent to a process chamber 704. In the particular configuration illustrated in FIG. 7A, extraction optics 10 is located on the side of the plasma chamber 102 and also borders the process chamber 704. When a plasma 712 is generated in the plasma chamber 102, an ion beam 710 may be extracted from extraction optics 10. The ion beam 710 may be formed by two ion beamlets that impinge on the substrate 708 at a non-zero angle symmetrically relative to a normal (referring to the Z-axis) to a major plane of the substrate 708 (referring to the XY plane in this example). In this way, with the aid of scanning the substrate holder 706 along the Y direction, the entire substrate 708 can be exposed to an elongated angled ribbon ion beam that covers the substrate 708 along the X axis (see FIG. 7B ). Furthermore, as shown in FIG. 7B , the substrate holder 706 can be movable along the Z direction to adjust the separation along the Z axis (Z gap) between the substrate 708 and the extraction plate 12, resulting in shaping the ion angular distribution (IAD) without affecting the energy of the ions impinging on the substrate.

[0037]

[0050] See Figures 3A-3E, which are a series of images showing the equipotential lines (electrostatic field lines 208) and the geometry of the ion beam 211 for the extraction optic 30 described above, with the Z-gap varying between different images. 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. While the results in Figures 3A-3E are for extraction optic 30, the results for extraction optics 10 and 50 are qualitatively similar. Note that the plasma density, electron temperature, and extraction voltage are all the same in Figures 3A-3E. It can be observed that the average angle of the ion beam 211 decreases as the z-gap length increases, even though the plasma density, electron temperature, and extraction voltage are the same. In other words, as the Z-gap increases, the angle of the ion beam 211 trajectory approaches the Z-axis direction. This result may be a result of the balance equation discussed above: as the Z gap increases, the electric field, which is approximately equal to the extraction voltage divided by the z gap length, decreases. The reduced electric field results in less penetration into the plasma, thus a less concave meniscus, which in turn results in a less tilted normal 216 (see FIG. 2B for an illustration of meniscus 214 and normal 216) relative to meniscus 214, ultimately resulting in a smaller average angle.

[0038]

[0051] The qualitative observations in Figures 3A-3E can be quantified using Figure 4A. Figure 4A shows the ion angular distribution (IAD) as a graph of beam current density as a function of the average angle relative to the Z-axis. The graph shows two distinct peaks (or sharp increases) in beam density symmetrically positioned around 0 degrees (representing the Z-axis). These distinct peaks represent the ion angular distribution (IAD) of the beam current of the two beamlets forming ion beam 211 extracted using extraction optics 30. The average angle of the IAD is measured relative to the normal (Z-axis direction) on the substrate. As the Z-spacing increases from 6 mm to 22 mm, the distribution of current density for the different cases shows a decrease in average angle from 37 degrees to 20 degrees. Furthermore, the separation of the beamlets on the wafer increases, as shown in Figure 4B, which is a graph of current density as a function of position along the Y-axis. Thus, Figure 4B shows the current density at the substrate as a function of position along the substrate. At 6 mm, the two beamlets overlap and their width can be estimated to be 2.5 mm. Increasing the Z-gap increases the separation but also decreases the beam width.

[0039]

[0052] See FIG. 5A, which is a graph showing the average angle of the ion beam produced by the extraction optics of the present embodiment as a function of Z-gap. Three different curves correspond to the geometries of extraction optic 10, extraction optic 30, and extraction optic 50. As can be seen, the average angle decreases monotonically with increasing Z-gap. For extraction optic 50, the average angle ranges from 17 degrees to 27 degrees. For extraction optic 10, the average angle shifts to higher angles, from 18 degrees to 32 degrees. For extraction optic 30, the distribution shifts to even higher angles, from 22 degrees to 37 degrees. FIG. 5B shows a comparison between modeled and experimentally measured IAD for variations in beam blocker 34, and the comparison shown shows very good agreement.

[0040]

[0053] It should be noted that the average angle can also be changed by varying the extraction voltage of the ion beam. However, varying the extraction voltage also changes the ion energy of the ion beam, which can completely shift the characteristics of the etching process and, in the case of high energies, may even be harmful to the substrate being processed. The voltages used in the modeling results disclosed herein correspond to the maximum extraction voltages used in plasma processing for practical applications. For lower extraction voltages, the curve in Figure 5A shifts downward. It should also be noted that an appropriate beam blocker can be selected based on specific application requirements. As a practical guideline, the beam blocker should provide an angular distribution with an average angle centered in the angular processing space.

[0041]

[0054] 6A-6C, which illustrate three different configurations of additional extraction optics according to further embodiments of the present disclosure. These embodiments are provided to address process throughput. To increase the etch rate of the substrate being processed, it is necessary to increase the overall extracted ion beam current. This increase in beam current can be achieved by increasing the number of extraction slits from two to four, as shown in extraction optics 600 of FIG. 6A.

[0042]

[0055] In this example, the cross-sectional side view shows extraction plate 602 with two extraction apertures, shown as extraction apertures 614. A boomerang-shaped beam blocker, shown as beam blocker 604, is positioned adjacent each extraction aperture, thereby defining four extraction slits, shown as extraction slits 616. Cooling channels 608 are also provided as shown, which may be created by gun drilling, a complex mechanical process used to create long channels, which may extend up to 400 mm or so. More generally, according to embodiments of the present disclosure, extraction optics may include a plurality of n extraction apertures, with a plurality of n beam blockers positioned to overlap the n extraction apertures, respectively, where n represents any suitable integer greater than 1.

[0043]

[0056] 6B and 6C, which illustrate an alternative configuration of a six-slit extraction optic. In FIG. 6B, extraction optic 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 positioned adjacent to each extraction aperture and overlaps with the apertures to define six extraction slits, shown as extraction slits 636. Cooling channels 628 are also provided as shown, and may be made by gun drilling.

[0044]

[0057] 6C , extraction optics 640 includes an extraction plate 642 with three extraction apertures, shown as extraction apertures 654. A curved, boomerang-shaped beam blocker, shown as beam blocker 644, is positioned adjacent each extraction aperture, thereby defining six extraction slits, shown as extraction slits 656. Cooling channels 648 are also provided, as shown, and may be created by welding small U-shaped structures to the bodies of beam blocker 644 and extraction plate 642, as shown. This method may be particularly useful for manufacturing very wide extraction optics, where the beam blocker and extraction plate may be elongated, measuring 300 mm, 400 mm, or more, and creating such long channels by gun drilling may be more difficult or time-consuming.

[0045]

[0058] In view of the above, the present disclosure provides at least the following advantages: i) the novel extraction apparatus disclosed herein allows for control of plasma chamber temperature and consequent gas temperature, which may reduce or eliminate wafer-to-wafer etch rate variations and process drift; ii) the extracted ion beam may have an IAD characterized by a mean angle similar to that of dielectric optics; and iii) the extracted beam current and consequent process throughput may be increased by increasing the number of slits without affecting chamber temperature control.

[0046]

[0059] While specific embodiments of the present disclosure have been described herein, the present disclosure is not limited thereto but is to the broadest possible scope within the skill of the art, and the specification can be read accordingly. Therefore, the above description should not be construed as limiting. Those skilled in the art will envision such modifications within the scope and spirit of the claims appended hereto.

Claims

1. 1. A processing system comprising: a plasma chamber; extraction optics positioned along a side of the plasma chamber, an extraction plate having an outer side and an inner side and defining at least one extraction aperture; a beam blocker overlapping the at least one extraction aperture and positioned toward an interior of the extraction plate; and Including, the beam blocker has a cross section defining a boomerang shape; the beam blocker comprises a first metallic material and the extraction plate comprises a second metallic material; extraction optics; a substrate platen disposed outside the plasma chamber and movable along a scanning direction relative to the at least one extraction aperture; A processing system comprising:

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

3. The processing system of claim 2 , wherein said at least one blocker cooling channel comprises a gundrill cooling channel and said at least one plate cooling channel comprises a gundrill cooling channel.

4. 3. The processing system of claim 2, wherein said at least one blocker cooling channel comprises a welded cooling channel and said at least one plate cooling channel comprises a welded cooling channel.

5. The processing system of claim 1 , wherein the boomerang shape is a rounded boomerang shape.

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

7. 2. The processing system of claim 1, wherein said beam blocker and said at least one extraction aperture are elongated along a first direction and define a pair of extraction slits elongated along said first direction.

8. 10. The processing system of claim 1, wherein said first metallic material and said second metallic material are aluminum.

9. 1. Extraction optics for an ion source, comprising: an extraction plate having an outer side and an inner side and defining at least one extraction aperture elongated along a first direction; a beam blocker overlapping the at least one extraction aperture, disposed toward an interior of the extraction plate, and elongated along the first direction, the beam blocker and the at least one extraction aperture defining a pair of extraction slits elongated along the first direction; Equipped with the beam blocker has a cross section that defines a boomerang shape in a plane perpendicular to the first direction; the beam blocker comprises a first metallic material and the extraction plate comprises a second metallic material; Extraction optics.

10. The extraction optic of claim 9 , wherein the first metallic material and the second metallic material comprise aluminum.

11. 10. The extraction optics of claim 9, wherein the at least one extraction aperture and the beam blocker are elongated along a first direction, the beam blocker includes at least one blocker cooling channel, and the extraction plate includes at least one plate cooling channel.

12. The extraction optic of claim 9 , wherein the boomerang shape comprises a rounded boomerang shape.

13. 10. The extraction optics of claim 9, wherein the at least one extraction aperture includes n plurality of extraction apertures, and n plurality of beam blockers are positioned to overlap the n plurality of extraction apertures, respectively.

14. The extraction optics of claim 11 , wherein the extraction plate is integrally connected to the beam blocker, and the at least one blocker cooling channel is fluidly coupled to the at least one plate cooling channel.

15. 1. A beam blocker for use in an ion source, comprising: a beam blocker body elongated along a first direction, the beam blocker body having a cross section defining a boomerang shape in a plane perpendicular to the first direction, the beam blocker body comprising a metallic material; a dielectric film coating disposed over a surface of the beam blocker and encapsulating the beam blocker body; A beam blocker comprising:

16. 16. The beam blocker of claim 15, wherein the boomerang shape comprises a rounded boomerang shape.

17. 17. The beam blocker of claim 16, wherein the exterior of the beam blocker includes a flat portion and a pair of curved portions adjacent to the flat portion.

18. 20. The beam blocker of claim 17, wherein the inside of the beam blocker is curved.

19. 16. The beam blocker of claim 15, wherein the metallic material comprises aluminum.

20. 16. The beam blocker of claim 15, wherein the beam blocker comprises at least one blocker cooling channel elongated along the first direction.

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