Plasma treatment apparatus

Abstract

Disclosed in the present invention is a plasma treatment apparatus, comprising: a vacuum chamber and a base located in the vacuum chamber; a dielectric window, which is located at the top of the vacuum chamber and arranged opposite to the base; a coil, which is at least partially located above the dielectric window and comprises at least two elongated excitation segments; a radio-frequency power supply, which applies a radio-frequency signal to the coil, enabling the current directions of the two excitation segments to be identical; and a rotation driving apparatus, which is used for driving the coil and / or the base to rotate, enabling the coil and the base to rotate relative to each other during a process. The coil structure provided by the present invention can improve the uniformity of electromagnetic field distribution and the utilization efficiency of the radio-frequency power supply.

Description

Plasma processing apparatus TECHNICAL FIELD

[0001] The present invention relates to a plasma processing apparatus, and more particularly, to an inductively coupled plasma processing apparatus. BACKGROUND

[0002] Etching or deposition using inductively coupled plasma is a key process for manufacturing semiconductor devices, including various microelectronic devices, thin film photovoltaic cells, light emitting diodes, etc. The basic process of plasma etching or deposition is that a reaction gas is introduced from a gas source into a reaction chamber, and is ionized and decomposed in plasma to form ions and free radicals. These highly reactive particles are transported by gas flow to the surface of the object to be processed for treatment or chemical reaction.

[0003] An inductively coupled plasma (ICP) chamber uses a coil to radiate radio frequency (RF) energy through a dielectric window into a vacuum chamber, thereby igniting and maintaining plasma in the gas. Typically, the ICP plasma chamber has one or more annular or spiral coils as the coil above the dielectric window at the top of the chamber. The magnetic field generated by such a circumferentially expanding coil often produces mutual inductance between different radius coil sections, resulting in more RF energy being concentrated in the outer region of the coil, thereby causing non-uniformity of plasma density. In addition, the ground or power terminals of the inductive coil are usually arranged at several points on the edge, and the positions of these terminals can also cause non-uniform distribution of plasma in the azimuthal angle. The non-uniformity of plasma density directly affects the uniformity of the surface treatment of the object to be processed. SUMMARY

[0004] The following summary of the invention is intended to provide an overview of some aspects and features of the invention. It is not intended to be exhaustive or to identify key or critical elements of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is to follow.

[0005] The present invention discloses a plasma processing apparatus, comprising: a vacuum chamber; a susceptor located in the vacuum chamber for carrying a substrate during a process; a dielectric window located at the top of the vacuum chamber and arranged opposite to the susceptor; a coil located at least partially above the dielectric window, comprising at least two longitudinal excitation segments; a radio frequency power source for applying a radio frequency signal to the coil, such that the current directions of the two excitation segments are in the same direction; a rotary drive device for driving the coil and / or the susceptor to rotate, so that the coil and the susceptor can be relatively rotated during the process.

[0006] Optionally, the electromagnetic field generated by the two excitation sections superimposes each other to generate an elongated plasma distribution above the substrate.

[0007] Optionally, the multiple excitation sections of the coil are connected in series or in parallel.

[0008] Optionally, the two excitation sections are arranged in parallel to each other.

[0009] Optionally, the length of the excitation section is greater than the diameter of the substrate.

[0010] Optionally, the length of the excitation section is greater than the diameter of the dielectric window.

[0011] Optionally, the coil comprises at least two excitation sections and a return section connecting two adjacent excitation sections, the return section and the excitation sections are located in different planes.

[0012] Optionally, the coil further comprises a height connection section connecting the excitation section and the return section, the height connection section makes the distance from the return section to the dielectric window greater than the distance from the excitation section to the dielectric window.

[0013] Optionally, the length of the height connection section is greater than 1 / 2 of the length of the excitation section.

[0014] Optionally, the excitation section comprises a center excitation section and edge excitation sections located on both sides of the center excitation section, the distance from the center excitation section to the dielectric window is greater than the distance from the edge excitation section to the dielectric window.

[0015] Optionally, the return section comprises a center return section and edge return sections located on both sides of the center section, the distance from the center return section to the dielectric window is less than the distance from the edge return section to the dielectric window.

[0016] Optionally, the radio frequency power supply supplies radio frequency signals to the coil through a non-contact coupler, the non-contact coupler comprises a transmitting end and a receiving end, the receiving end is electrically connected to the input end of the coil, and the transmitting end is electrically connected to the radio frequency power supply.

[0017] Optionally, the receiving end rotates synchronously with the coil, and the receiving end rotates oppositely with the transmitting end.

[0018] Optionally, at least one of the receiving end and the transmitting end is a ring-shaped conductor.

[0019] Optionally, the radio frequency power supply supplies radio frequency signals to the coil through a brush.

[0020] Optionally, the lengths of the excitation sections are equal or unequal.

[0021] Optionally, the coil is connected with a rotating shaft, and the rotating drive device drives the rotating shaft to drive the coil to rotate.

[0022] Optionally, the rotating drive device is an electric motor.

[0023] Optionally, the dielectric window is dome-shaped, and the exciting section of the coil is a curved section.

[0024] Optionally, the dielectric window is cylindrical.

[0025] Aspects disclosed herein relate to an inductively coupled plasma chamber with a rotating coil or a rotating pedestal, in which RF power is transmitted to the coil by implementing a non-contact DC break / RF short mechanism. The non-contact DC break / RF short mechanism forms an ohmic break, preventing DC current flow while allowing RF power transmission. This configuration can be referred to herein as a non-contact coupler or a non-contact capacitive coupler.

[0026] Disclosed embodiments provide a non-contact DC break / RF short mechanism having two electrical contacts that are physically separated from each other, such that the contacts do not physically touch each other. The two electrical contacts are configured to form a DC break while allowing RF power to flow through, thereby forming an RF short.

[0027] In disclosed embodiments, a plasma processing chamber is provided, including: a vacuum chamber having a dielectric window; a coil provided around the dielectric window, the coil having an input terminal and at least one ground terminal; an electric motor connected with the coil for applying a rotating force to the coil; an RF power source; and a non-contact coupler receiving RF power from the RF power source and applying the RF power through the input terminal of the coil.

[0028] Disclosed embodiments also include a plasma processing chamber, including: a vacuum chamber; a pedestal disposed on a floor of the vacuum chamber, configured to support a substrate; a dielectric window disposed at an upper portion of the vacuum chamber; a coil disposed around the dielectric window, the coil including a plurality of straight exciting sections arranged parallel to a plane of the dielectric window, the plurality of straight exciting sections being parallel to each other and spaced apart to cause superposition of electromagnetic radiation of any two of the plurality of exciting sections; and an electric motor to cause relative rotation between the substrate and the coil. The plurality of exciting sections can have the same or different lengths. The plurality of exciting sections can be connected in series or in parallel. Current can flow in the same direction in all of the plurality of exciting sections. The coil can be connected to an RF power source through a capacitive coupler. The coil can further include a rotating shaft connected to the electric motor, and all of the plurality of exciting sections are connected to the rotating shaft. The coil can be connected to the RF power source through a capacitive coupler having a stationary contact and a rotating contact connected to the coil.

[0029] Aspects of the invention relate to an apparatus for applying radio frequency energy to a process chamber, comprising: a coil having a main shaft rotatable about an axis of rotation, an input for receiving radio frequency power, and an output for grounding; a non-contact coupler having an input connected to the coil and a transmission connector connected to a radio frequency power source, the input and the transmission connector configured to allow radio frequency power to flow therethrough while forming a direct current break, the input rotatable relative to the transmission connector; and a ground coupler connected between the output of the coil and a ground potential. The ground coupler allows radio frequency power to flow therethrough while forming a direct current break. The input can comprise an inner conductive ring, and the transmission connector comprises an outer conductive ring concentric with the inner conductive ring and defining a separation space between the inner conductive ring and the outer conductive ring, thereby enabling capacitive coupling of radio frequency energy between the inner conductive ring and the outer conductive ring. The inner conductive ring rotates with the coil, and the outer conductive ring is stationary. The apparatus can further comprise a dielectric ring concentric with the inner conductive ring and positioned within the separation space. The dielectric ring can be made of ceramic, Teflon, or other similar materials. The apparatus can further comprise a bearing rotatably supporting the main shaft, and a motor connected to the main shaft and applying a rotational force to the main shaft.

[0030] The coil can comprise a plurality of excitation segments arranged in a horizontal plane. The plurality of excitation segments can be connected in series to form a plurality of rectangular coils, and at least two of the plurality of rectangular coils can have different lengths. The plurality of excitation segments can also be connected in parallel, and at least two of the plurality of excitation segments can have different lengths. The coil can further comprise a plurality of curved excitation segments arranged in a horizontal plane or a dome shape.

[0031] Aspects of the invention include a plasma processing chamber, comprising: a vacuum chamber; a pedestal on a floor of the vacuum chamber; a dielectric window on an upper portion of the vacuum chamber; a coil disposed around the dielectric window, the coil attached to a rotatable shaft; a motor connected to the rotatable shaft; a radio frequency power source; and a non-contact coupler capacitively coupling radio frequency energy transmitted from the radio frequency power source to the coil; wherein the non-contact coupler comprises a capacitor having an input contact connected to the radio frequency power source and an output contact connected to the coil, the input contact rotatable relative to the output contact.

[0032] The disclosed plasma processing apparatus solves the problem of inconsistent electromagnetic field strength at different radii in the prior art by configuring the excitation segments of the coil to be elongated, and the excitation segments are closer to the dielectric window than the return segments, thereby avoiding the cancellation of the electromagnetic field generated by the return segments on the excitation segments, greatly improving the utilization efficiency of the radio frequency power source. The present invention further improves the uniformity of the plasma distribution above the substrate by driving the coil or the pedestal to rotate during the process through a rotary drive device. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and, together with the description, explain the principles of the application. The drawings are intended for illustrative purposes only and are not intended to limit the scope of the application in any way. The drawings are intended to illustrate major features of the embodiments in a diagrammatic mode so as not to obscure the principles of the present application. The drawings are not intended to be drawn to scale in any respect, and are not intended to show relative dimensions of the depicted elements or relative sizes of the depicted elements.

[0034] Figure 1 is a schematic cross-sectional view of a plasma chamber according to one embodiment.

[0035] Figures 1A through 1F illustrate various embodiments of a rotatable non-contact coupler.

[0036] Figures 2A through 2G illustrate embodiments of various shapes of coils.

[0037] Figures 3A and 3B schematically illustrate an isometric view and a top view, respectively, of a rotatable coil.

[0038] Figure 4 schematically illustrates a top view of yet another embodiment of a rotatable coil.

[0039] Figure 5 illustrates an embodiment of a plasma chamber having a curved dielectric window.

[0040] Figure 6 is a block diagram of a process flow according to one embodiment.

[0041] Figure 7 schematically illustrates a cross-sectional view of another processing chamber embodiment. DETAILED DESCRIPTION

[0042] A plasma processing apparatus according to the present application is further described below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present application will become apparent to those skilled in the art from the following description of the various embodiments. It is to be understood that the drawings are designed solely for purposes of illustration to aid in the description of the various embodiments, and changes in the depicted structures, proportions, dimensions, etc. can be made to the drawings and electronic components in the drawings shown, and in the presently disclosed technology and yet be encompassed by the application and the concept of the application. Any structural, proportional or size changes that do not affect the functionality of the application and which are within the ability of one of ordinary skill in the art are contemplated by the present application and are encompassed by the presently disclosed technology.

[0043] As described in the background section, the coil on the dielectric window on the top of the ICP plasma chamber is usually set as a ring or spiral shape, and the magnetic field generated by this circumferentially expanded coil usually produces mutual inductance between the coil parts of different radii, resulting in uneven plasma distribution at different radii in the reaction chamber, and further causing unevenness in the processing of the substrate. To solve this technical problem, the coil above the dielectric window is set as a double-layer structure, including an excitation segment layer close to the dielectric window and a return segment layer above the excitation segment layer. When a radio frequency signal is applied to the coil structure, the utilization efficiency of the radio frequency signal can be greatly improved because the excitation segment layer is closer to the reaction chamber, and the current directions of the multiple excitation segments are the same, and the electromagnetic signals induced by the multiple excitation segments in the reaction chamber superimpose on each other. When the substrate is processed in the reaction chamber, by controlling the relative rotation between the coil and the substrate, a uniform plasma distribution can be generated on the surface of the substrate, and the substrate can be uniformly processed by the plasma.

[0044] Figure 1 shows a schematic diagram of a plasma processing device structure, including a vacuum chamber 100 and a dielectric window 105 arranged on the top of the vacuum chamber 100. A coil 120 is arranged above the dielectric window. Unlike the traditional planar spiral coil, the coil 120 of the present application includes an excitation segment layer close to the dielectric window and a return segment layer above the excitation segment layer. The excitation segment layer includes at least two substantially parallel longitudinal strip-shaped excitation segments 126. Two adjacent excitation segments are connected by a height connecting segment 130 and a return segment 132, so that each excitation segment 126 has the same current direction. When a radio frequency signal is applied to the coil 120, the electromagnetic signals induced by the multiple excitation segments 126 with the same current direction in the reaction chamber superimpose on each other, generating a longitudinal electromagnetic field distribution.

[0045] In order to obtain a more uniform plasma distribution, the present application provides a rotation driving mechanism to realize the relative rotation between the coil 120 and the susceptor 115. As shown in Figure 1, a rotation driving device such as a motor 141 can be arranged below the susceptor to realize the rotation driving of the susceptor. A rotation driving device can also be arranged on the coil, or both the susceptor and the coil are provided with a rotation mechanism. Since the coil needs to be connected to the radio frequency power supply, its rotation mechanism is more complex, which will be described in detail below in conjunction with the drawings.

[0046] In order to generate a uniform plasma distribution above the substrate, the excitation segments 126 of the coil 120 can be arranged as parallel straight segments. Of course, the excitation segments 126 can also be arranged as substantially long strip-shaped curves in other embodiments. Preferably, the bending degrees of the adjacent curved excitation segments are close.

[0047] According to the above description, when the RF signals with the same current direction are input into the multiple exciting sections, the superimposed electromagnetic field distribution is generated in the reaction chamber, the length of the electromagnetic field distribution can be determined by the length of the exciting section, and the width of the electromagnetic field distribution can be determined by the distance of the exciting sections with the largest spacing distance. Therefore, in order to allow the edge region and the central region of the substrate to be uniformly treated by the plasma, the length of the exciting section 126 can be set to be greater than the diameter of the substrate 110. Further, when the length of the exciting section 126 is greater than the diameter of the dielectric window 105, a longer electromagnetic field distribution can be obtained. When the distance of the exciting sections with the largest spacing distance is greater than the diameter of the substrate or even greater than the diameter of the dielectric window, the electromagnetic field formed by the coil 120 in the reaction chamber is in the shape of a longitudinal or square distribution that fully covers the substrate, so that the surface of the substrate can be uniformly treated by the plasma.

[0048] The electromagnetic field distribution in the reaction chamber is not only affected by the exciting section 126 but also affected by the return section 132. Since the current direction of the return section 132 is opposite to the current direction of the exciting section 126, the electromagnetic field generated by the return section 132 in the reaction chamber can offset the electromagnetic field generated by the exciting section 126 in the reaction chamber. In order to minimize the offset effect of the electromagnetic field, the height connection section 130 is arranged between the return section and the exciting section in the present application. The height connection section 130 is preferably arranged in the vertical direction, so that the return section 132 and the exciting section 126 are located in different planes. Alternatively, when the length of the height connection section 130 is greater than 1 / 2 of the length of the exciting section 126, the offset effect of the electromagnetic field generated by the return section 132 and the exciting section 126 in the reaction chamber can be significantly reduced, thereby improving the energy utilization rate of the RF power source and avoiding the non-uniform distribution of the plasma caused by the different offset effects of the return sections 132 at different positions. In another embodiment, the height connection section 130 can also be arranged in a non-vertical direction. As long as the height of the return section layer and the height of the exciting section layer can be adjusted, the purpose of the present application can be achieved.

[0049] When the coil 120 is powered, the electromagnetic field intensity generated by the exciting section directly below the coil 120 is strong, and the electromagnetic field intensity between the two exciting sections is slightly weak. Therefore, the electromagnetic field intensity below the coil 120 is not absolutely uniform. In order to ensure the uniformity of the substrate treatment, rotation is needed to compensate. The rotation can be the rotation of the susceptor or the rotation of the coil. The embodiments of the coil rotation of the present application will be described below with reference to the accompanying drawings. Different embodiments or their combinations can be used for different applications or to achieve different benefits. According to the results to be achieved, different features disclosed herein can be used alone or in combination with other features as needed, balancing the advantages and needs and constraints.

[0050] Figure IE is a cross-sectional schematic view of a plasma chamber having a rotating coil 120, according to an embodiment. The vacuum chamber 100 includes a dielectric window 105 as a ceiling. A substrate 110 to be processed is placed on a pedestal 115 within the vacuum chamber 100. Plasma is ignited and sustained within the vacuum chamber 100 by applying RF energy to the rotatable coil 120 (the direction of rotation is indicated by the counterclockwise curved arrow, but the direction of rotation can be clockwise, with similar results). The coil 120 can be placed directly on the dielectric window, or can be placed at a distance from the dielectric window. In this example, the coil 120 includes horizontal, window-parallel excitation segments 126 and a plurality of vertical, height- connecting segments 130. One or more of the height-connecting segments 130 are physically and electrically connected to a spindle 133. Rotation of the coil 120 is effected by coupling (indicated by dashed lines) a motor 139 to the spindle 133. RF power is applied to the coil 120 from an RF power source 140 through an input port (sometimes referred to as a hot-side connector), in this embodiment formed by a non-contact coupler 135. Incidentally, since RF energy is transmitted through the non-contact coupler without ohmic contact between the signal input and output, the non-contact coupler can be considered a form of transformer, although the signal passing through it is not changed.

[0051] A non-contact coupler according to the present invention has a receiving connector (hereinafter referred to as an inner contact point) connected to an input of a coil and a transmitting connector (hereinafter referred to as an outer contact point) coupled to an RF power source, the receiving connector and the transmitting connector being non-contact coupled such that a direct current is broken between them while allowing transmission of RF power, the receiving connector being rotatable relative to the transmitting connector; and further includes a ground coupler connected between an output of the coil and a ground potential.

[0052] In the embodiment of Figure 1 E, the non-contact coupler 135 is formed as a DC break / RF short, i.e. the non-contact coupler consists of two spatially separated contact points that are not in direct physical or electrical contact, where the two contact points can be relatively rotated, e.g. the outer contact point is stationary and the inner contact point is rotatable. In the embodiment shown in Figure 1 E, this is achieved by manufacturing the non-contact coupler to have an inner contact point 134 (shown as a conductive ring in Figure 1 E) and an outer contact point (shown as a conductive ring 136 in Figure 1 E). In this embodiment the outer contact point 136 is stationary and the inner contact point 134 is rotatable. As shown in the top view outlined in dashed lines, the inner contact point 134 (conductive ring) and the outer contact point 136 (larger conductive ring) are coaxial with a space 137 in between, so they are not in physical or electrical contact and allow relative rotation. On the other hand, the inner contact point 134 is electrically connected to the main shaft 133, which is coaxial with the inner contact point 134 and the outer contact point 136. In this embodiment, the inner contact point 134 is an inner conductive ring and the outer contact point 136 is an outer conductive ring. Here, the outer conductive ring 136 is stationary and the inner conductive ring 134 rotates with the shaft 133.

[0053] With the specific arrangement shown in Figure 1 E, the inner conductive ring 134 and the outer conductive ring 136 form a capacitor, so RF energy can pass through the space 137 by capacitive coupling, i.e. a RF short is formed. On the contrary, DC current cannot flow from the outer conductive ring 136 to the inner conductive ring 134, so a DC break is formed. The space 137 outlined in dashed lines is only occupied by air. On the contrary, as outlined in dotted lines, the space 137 can be filled with a dielectric material 138, e.g. a ceramic ring, etc., to increase the dielectric constant of the capacitor formed by the inner and outer rings, so as to improve the transmission of RF energy. The dielectric material can fill the space 137 completely or partially. In one example, the dielectric material 138 is placed in the space 137 so that the arrangement also serves as a rotational bearing for the main shaft 133. Alternatively, a separate rotational bearing 132 can also be installed on the shaft 133 to ensure stable axial rotation of the motor 139.

[0054] FIGS. 1A-1D show different embodiments of the non-contact coupler, where one of the inner and outer contacts forms one or more arcs instead of a full circle. In FIG. 1A, the inner contact 134 forms one arc, here a semicircle, but can cover an angle smaller or larger than a semicircle (180 degrees). In FIG. IB, the inner contact 134 forms two arcs, while in FIG. 1C the outer contact 136 forms two arcs. It can be seen that either the inner or the outer contact can form one or more arc-shaped contacts. FIG. ID shows an embodiment of the inner contact 134, where multiple arcs are attached to a support cylinder 131 to enhance the mechanical stability of the inner contact 134. The support cylinder can be made of an insulating material and can be fixed to the main shaft 133 or serve as a rotating bearing on the main shaft 133.

[0055] One or more height segments 130 can be used to ground the coil 120 to complete the RF circuit. In the embodiment of FIG. IE, this is also achieved by a non-contact coupler with an inner ground ring 144 and an outer ground ring 146. The inner ground ring 144 rotates with the coil 120, while the outer ground ring 146 is stationary. Again, the inner ground ring 144 does not contact the outer ground ring 146, and the space between the inner ground ring 144 and the outer ground ring 146 can be occupied by air or a ring made of a dielectric material (e.g., ceramic, glass, etc.).

[0056] In the disclosed embodiments, since the RF energy is transferred to the coil by capacitive coupling, the problems associated with traditional contacts are avoided. For example, no particles are generated, the RF energy is transferred smoothly by capacitive coupling, and thus there are no spikes and / or arcing and / or unstable impedance, etc. advantages. Thus, a stable plasma can be maintained within the vacuum chamber. In further embodiments, the electrical connection can also be achieved by brushes or the like while the coil 120 is rotating.

[0057] The disclosed embodiment according to FIG. IE provides a schematic diagram of a plasma processing apparatus having a pedestal to support a substrate within a vacuum chamber; the vacuum chamber is provided with a dielectric window at the ceiling, the dielectric window is located in a horizontal plane; a rotating coil is disposed above the dielectric window, the rotating coil comprises: a main shaft rotating around an axis, an input port and a ground port; wherein both the input port and the ground port are formed by a non-contact capacitive coupling connector. In the embodiment of FIG. IE, the non-contact capacitive coupling connector is formed by a receiving ring electrically connected to the main shaft and a transmitting ring coupled to an RF power source, the RF energy flows through capacitive coupling through an insulating space between the transmitting ring and the receiving ring. In some embodiments, the insulating space is occupied by air, while in other embodiments, the insulating space is occupied by a dielectric material (e.g., a dielectric ring).

[0058] ​In the embodiment of FIG. IE, the rotating coil rotates around a spindle connected to a receiving ring coaxial with the spindle and rotating with the spindle, the receiving ring made of electrically conductive material; a transmitting ring made of electrically conductive material positioned coaxially with the receiving ring and defining an insulating gap between the input ring and the receiving ring, the transmitting ring coupled to a radio frequency power source, the radio frequency signal passing through the insulating gap between the input ring and the receiving ring by capacitive coupling; the coil further comprising an excitation segment connected to the spindle and parallel to the ceiling plane, the excitation segment radiating radio frequency energy received from the spindle; and a grounding port connected to the radiating coil, the grounding port comprising a rotating ring connected to the radiating coil and rotating coaxially with the spindle, and a fixed ring coaxial with the rotating ring, the fixed ring defining a second insulating space between the rotating ring and the fixed ring, the fixed ring connected to ground potential.

[0059] FIG. IF shows a schematic diagram of the electrical connections of another embodiment of the coil. Unlike the embodiment of FIG. IE in which the excitation segment receives radio frequency energy from the spindle, the embodiment of FIG. IF does not have an apparent spindle structure, and both the input (I In) and the output (I Out) of the radio frequency energy are from the edge region of the coil. In this embodiment, a high connection segment (not shown in the figure) connected to the excitation segment is fixedly connected to the inner conductive ring 134, and the outer conductive ring 136 and the inner conductive ring 134 can rotate relative to each other; similarly, a high connection segment 130 can be used to ground the coil 120 to complete the radio frequency circuit. In the embodiment of FIG. IF, this is also achieved by a non-contact coupler having an inner ground ring 144 and an outer ground ring 146. The inner ground ring 144 rotates with the coil 120, while the outer ground ring 146 is fixed. The deformed arrangement of the inner conductive ring 134 and the outer conductive ring 136 and the inner ground ring 144 and the outer ground ring 146 of FIG. IF can refer to FIGS. 1A-1D, and will not be described again here.

[0060] In the context of the present disclosure, the term "ground potential" refers to any common reference voltage potential of the plasma chamber, which can or can not be the earth (zero) potential.

[0061] Coil 120 can form various shapes. Figures 2A-2F schematically illustrate embodiments of coils of different shapes, where only elements relevant to the flow of radio frequency energy are shown, and mechanical and / or structural details are omitted to maintain clarity. In the embodiments of Figures 2A-2D, coil 120 includes at least two excitation segments 126 arranged in parallel to the dielectric window and to each other, and a height connection segment coupling the coil to the radio frequency power source. The height connection segment can include a vertical connector, generally perpendicular to the plane of the excitation segments and directed away from the plane of the excitation segments, i.e., away from the plane of the dielectric window. The height connection segment can also include return segments 132, which lie in a plane parallel to the plane of the excitation segments, but further away from the dielectric window. With these arrangements, the dielectric window is located at a relatively uniform distance from the magnetic field generated by the large-sized induction coil. Thus, the rotating induction coil ignites and sustains plasma uniformly within the vacuum chamber. Furthermore, any return segments are placed in a plane sufficiently far from the dielectric window so as not to interfere with the plasma sustained by the coil. Thus, only the excitation segments near the window can effectively sustain plasma within the vacuum chamber, and these excitation segments can be referred to as the drive coil, while the other conductors act as various connectors.

[0062] Figure 2A illustrates a coil layout in which the coil is composed of multiple straight (linear) excitation segments 126 arranged in parallel, composed of straight wires and lying in a plane parallel to the plane of the dielectric window, forming an excitation segment layer. Each excitation segment 126 is connected at one end to a vertical height connection segment, and multiple return segments 132, parallel to each other and lying in a plane parallel to the plane of the dielectric window and at a distance greater than the distance of the plane of the coil, are connected at one end to the vertical height connection segment 130. This connection scheme connects all excitation segments 126 in series, thus having one input end I in and one ground end I out. The excitation segment layer is located sufficiently close to the plane of the dielectric window so that only the excitation segments 126 of the coil can effectively generate plasma within the chamber, and these excitation segments can be identified as the drive coil, while other parts of the coil act as various connectors, where the plane location of the return segments 132 is sufficiently far from the window plane so that their effect on the plasma is negligible or non-existent. Furthermore, in this embodiment, all straight excitation segments 126 are of the same length, and preferably longer than the diameter of the substrate to be processed within the plasma chamber.

[0063] Another embodiment of a rotatable coil is shown in FIG. 2B, where multiple coils are connected in series, with the straight excitation segments 126 having different lengths. As shown in FIG. 2B, the straight excitation segments 126 are located in a plane parallel to the plane of the dielectric window, and are connected in series with the RF power source through vertical height connecting segments 130 and return segments 132. This configuration can be used to control the plasma density at different radii inside the vacuum chamber. In this particular embodiment, at least one excitation segment 126 spans the entire diameter of the dielectric window 105, and can in fact extend beyond the diameter of the window 105. In contrast, the lengths of the remaining straight excitation segments 126 are shorter than the central excitation segment, with each excitation segment gradually decreasing in length, shorter than the radius of the substrate. In the embodiment shown, the excitation segments are arranged such that more RF energy is generated at the peripheral region of the substrate, thereby increasing the plasma density at the periphery. This configuration is beneficial when the structure of the vacuum chamber naturally results in a lower plasma density at the periphery, so that the higher RF energy at the periphery can balance the uniformity of the plasma.

[0064] In FIG. 2B, each excitation segment 126, together with the height connecting segment 130 and return segment 132 connected to it, forms a rectangular inductive coil, as shown in the boxed portion of FIG. 2B. Each inductive coil is of different size, so that the plasma generated by each inductive coil in each cycle of the coil corresponds to a different region of the plasma, and the plasma density generated by the superposition of the multiple horizontal inductive coils is optimally distributed. The size and position of each inductive coil can be configured for each plasma chamber to achieve the optimal plasma distribution. For example, different vacuum chambers and different plasma processes can require different plasma density distributions, and the desired plasma distribution can be achieved by adjusting the size and position of each inductive coil.

[0065] FIG. 2C schematically illustrates an embodiment of an RF coil that is electrically connected by a set of rectangular inductive coils 126a-126c (see boxed portion) and mechanically fixed together to rotate as a whole around a main shaft 133. By connecting multiple coils in parallel, the inductance value can be significantly reduced, and the drive current can be increased. The central coil 126a covering the center of the dielectric window 105 has the largest size, i.e., length, while the coils 126b and 126c covering the edge regions can be shorter in length. As long as the two ends of each drive coil extend beyond the dielectric window 105, the uniformity of the plasma below can be ensured. In another embodiment, the lengths of the multiple excitation segments connected in parallel can also be equal, and mechanically fixed together to rotate, without a distinct main shaft structure.

[0066] In the embodiment shown in FIG. 2C, the excitation segments 126 are connected in parallel, so each rectangular coil 126a-126c is independently connected to the radio frequency input and ground. In addition, as shown by the arrows in FIG. 2C, the current flow in each excitation segment 126 is in the same direction. In the specific embodiment shown in FIG. 2C, the input terminals of all the induction coils are arranged on one side, while all the ground terminals are arranged on the other side. When multiple excitation segments 126 are connected in parallel, the parallel excitation segments can be connected to different inner contact points 134 through height connection segments of different heights. The inner contact points can be in a ring structure or an arc structure. In another embodiment, multiple parallel excitation segments can also be connected to the same ring or arc inner contact point, as shown in FIG. 2D. In this embodiment, the lengths of the excitation segments or height connection segments at different positions to the inner conductive ring 134 are slightly different to ensure good electrical connection with the inner conductive ring. FIG. 2D is a schematic diagram of the electrical connection of the structure shown in FIG. 2C. The specific arrangement is similar to that of FIG. IF, which will not be described here.

[0067] In the embodiments shown in FIGS. 2A-2D, the excitation segments 126 are located in the same plane and parallel to each other. The distance between the excitation segments is configured to ensure that the electromagnetic fields generated by two adjacent excitation segments superimpose. Through this arrangement with superimposed electromagnetic fields of two adjacent excitation segments, the uniformity of the plasma can be enhanced through relative rotation between the coil and the substrate. As shown in FIGS. IE and IF, the relative rotation can be achieved by rotating the coil 120. On the other hand, the relative rotation can be achieved by rotating the substrate, for example, by rotating the support (e.g., chuck) of the substrate through the optional motor 141.

[0068] The above embodiments disclose the setting of the excitation segments in the same plane. Fig. 2E discloses a schematic diagram of the excitation segments in different planes. It is found that in some applications, the electromagnetic field intensity generated by the coil 120 tends to be stronger in the central region than in the edge region. By setting the excitation segments to include a central excitation segment 126m and edge excitation segments 126e located on both sides of the central excitation segment, and setting the distance from the central excitation segment 126m to the dielectric window to be greater than the distance from the edge excitation segments 126e to the dielectric window, the electromagnetic field intensity generated by the central excitation segment is appropriately weakened, and the uniformity of the central region and the edge region as a whole is achieved. The height difference between the central excitation segment 126m and the edge excitation segments 126e to the dielectric window can be set as needed. According to the same principle, Fig. 2F provides another variant embodiment, by setting the return segments 132 to be a central return segment 132m and edge return segments 132e, and setting the distance from the central return segment 132m to the dielectric window to be less than the distance from the edge return segments 132e to the dielectric window, the electromagnetic field generated by the central return segment 132m is appropriately enhanced to cancel out the electromagnetic field generated by the central excitation segment 126m, and the uniformity of the central region and the edge region as a whole is achieved. In another embodiment, the excitation segments 126 and the return segments can be set to have central segments and return segments close to each other, which will not be described here.

[0069] Fig. 2G shows another embodiment of a coil. In this embodiment, the excitation segments and the return segments are located in the same plane, and the current flows in each adjacent excitation segment and return segment in an alternating direction. Although this embodiment will lose part of the radio frequency power efficiency, due to the electromagnetic field cancellation and superposition of the excitation segments and the return segments, a better uniformity of the electromagnetic field distribution can be obtained.

[0070] Figs. 3A and 3B schematically show an isometric view and a top view of a rotatable coil 120, respectively. In this embodiment, the coil is composed of a plurality of parallelly connected horizontal drive coils, which have different positions, directions and lengths. The arrangement shown in Figs. 3A and 3B is configured to increase the plasma concentration as the radius increases from the axis. By rotating such a coil, the plasma density in the chamber can be balanced.

[0071] Figure 4 schematically illustrates a top view of another rotatable coil 120. The coil in Figure 4 is composed of multiple curved excitation segments 126, arranged in a rotationally symmetric fashion, and connected at one end to a main shaft 133. In this embodiment, each excitation segment 126 has a curved branch 127 extending therefrom. In Figure 4, the coil has three main excitation segments 126, each with a branch 127, but the number of main excitation segments and branches can be designed according to the desired plasma distribution and density. As with other embodiments, RF energy is coupled to the main shaft 133 by capacitive coupling, and ground is coupled through the ends of the excitation segments 126 and branches 127. In this regard, while in most of the description it is suggested that both the RF feed and ground be coupled to the coil by capacitive coupling, it is also possible for the RF feed to be coupled by capacitive coupling, while ground is coupled by ohmic contact. For example, the RF feed can be coupled by capacitive coupling using any of the non-contact couplers disclosed herein, while ground can be coupled by ohmic contact using a brush.

[0072] Plasma will naturally seek pressure equilibrium within the vacuum chamber, so the natural distribution of plasma is spherical. In addition, silicon substrates are typically circular planar wafers due to the crystal growth of silicon. However, glass substrates are typically rectangular. With this in mind, designers typically design the plasma chamber with circular sidewalls so that the plasma within the vacuum chamber "sees" circular symmetry. Since the substrates are planar, the susceptor that supports the substrates is also planar, resulting in a planar floor design. To facilitate manufacturing and reduce cost, the dielectric ceiling is also made planar, as shown in Figure 1. However, forcing the plasma to "squeeze" between the planar substrates and ceiling results in increased density at the center of the plasma. To address this issue, some chambers use a dome-shaped ceiling, as shown in Figure 5.

[0073] Figure 5 illustrates an embodiment of a plasma chamber with a dome-shaped curved dielectric window. The plasma chamber has sidewalls 500, which can be cylindrical. A susceptor 510 is located on the floor of the chamber to support one or more substrates 515. A curved dielectric window 505 is located above the sidewalls to complete the vacuum chamber in which the plasma 501 is ignited. In this embodiment, the dielectric window is shaped like a dome or a vault. A curved rotatable coil 525 is located above the dielectric window 505, and the placement of the excitation segments generally follows the shape of the dielectric window as curved lines that are parallel to each other. The coil includes a main shaft 533 that is connected to a motor 539. RF energy is delivered from an RF power source 540 through a matching circuit 541 and then capacitively coupled to the coil 525 through a non-contact coupler 535. Note that the matching circuit 541 can be used in any of the embodiments disclosed herein.

[0074] In the embodiment of Figure 5, and in any other embodiment disclosed herein, there are multiple ways to construct the non-contact coupler. The boxed portion of Figure 5 illustrates two examples, which can be used in any other embodiment. In the right boxed portion, a non-contact coupler 535 is illustrated, which has an inner ring 534 that is physically connected to the spindle 533 to rotate with it. An inner dielectric ring 538 is provided above the inner ring 534, and an outer ring 536 is provided above the dielectric ring. The inner dielectric ring rotates with the spindle 533, while the outer ring 536 is stationary. The outer ring 536 is connected to the RF power source 540 through a matching circuit 541, and the RF energy is capacitively coupled to the inner ring through the dielectric ring 538. In this way, the non-contact coupler 535 also serves as a rotational bearing for the spindle 533.

[0075] The left boxed portion of Figure 5 illustrates another embodiment of a non-contact coupler. According to this embodiment, the non-contact coupler is simplified by eliminating the inner ring. Here, the spindle 533 itself serves as the inner ring, and thus the dielectric ring 538 is provided above the spindle 533 and also serves as a rotational bearing. The outer ring 536 is provided above the dielectric ring 538 and directly capacitively couples the RF energy to the spindle 533.

[0076] The coil 525 shown in Figure 5 can be grounded with any conventional rotational connector, such as a brush, but Figure 5 shows the coil 535 grounded through another non-contact coupler 535g. The non-contact coupler is composed of an inner ring 544 that rotates with the coil 525 and an outer ring 546 that is stationary. The outer ring 546 is ohmically connected to ground and is coaxial with the inner ring 544 to form a capacitive coupling of RF energy.

[0077] As can be appreciated from the disclosure, by rotating the induction coil, the plasma concentration under the dielectric window has the same concentration at different azimuthal angles. By choosing the appropriate horizontal drive coil pattern, uniform plasma concentration can be achieved in the radial direction. Ultimately, the plasma concentration uniformity inside the reaction chamber is significantly higher than conventional techniques that use multiple stationary ring coils or spiral coils. By coupling the RF energy onto the coil through capacitive coupling, the energy transfer is uniform, and thus a stable plasma can be maintained. Furthermore, when using a non-contact coupler, the generation of particles is avoided, and the service life of the rotatable coil is extended.

[0078] The present disclosure also discloses a method of operating a plasma chamber, as shown in FIG. 6. The process begins at step 600 by inserting a substrate into the chamber. At step 605, process gas is injected into the chamber, and at step 610, the coil motor is activated to rotate the coil. At step 615, the RF power is activated to capacitively couple RF energy to the coil to ignite and sustain a plasma within the chamber. When the process time is complete, the RF energy is turned off to extinguish the plasma at step 620, and any remaining exhaust is pumped from the chamber at step 625. The processed wafer is removed at step 630, and the process is repeated for the next substrate. Note that the order of the process steps described herein is not mandatory, and the order of certain steps can be changed, and other steps can be added. For example, a step can be added to apply a chuck voltage to the chuck to clamp the substrate. Also, although a step is mentioned to pump down the chamber, in fact the chamber is pumped down throughout the process of injecting process gas into the chamber to remove exhaust.

[0079] FIG. 7 illustrates another embodiment of a processing chamber having a rotatable coil. Elements in the embodiment of FIG. 7 that are similar to FIG. 5 are identified using the same reference numbers, and are not described again here. The embodiment of FIG. 7 differs from other embodiments disclosed herein in that the upper portion of the vacuum chamber includes a dielectric window 706 that forms a portion of or extends from the sidewall 500. The dielectric window 706 can be cylindrical, and can terminate at a ceiling 707. The ceiling 707 can be a flat circular disk, and can be made of a dielectric material, as shown by the dashed line. If the ceiling 707 is made of a dielectric material, it can be integrally manufactured with the cylindrical dielectric window 706. The coil 725 is made to extend downward so as to rotate around the dielectric window 706. The coil 725 is connected to the shaft 533 as shown, and is rotated by the motor 539, as in other embodiments disclosed herein.

[0080] Another feature that can be implemented in any of the other embodiments shown herein is shown in FIG. 7, which is the use of a belt drive system to transmit rotation to the coil. This can be used to avoid any RF energy from flowing into the motor 739. In this arrangement, the motor can be mounted separately and remotely, and uses a belt 731 to transmit rotational motion to the shaft 733.

[0081] The boxed portion in FIG. 7 illustrates another feature that can be implemented in any of the embodiments disclosed herein, in which the inner ring 734 and the outer ring 736 are configured as the inner race and outer race of a ball bearing, and the dielectric isolator is formed by the balls 738 made of a dielectric material. The balls can also sit in a cage made of a dielectric material. In this case, although reference is generally made to balls of a ball bearing, it should be understood that this reference includes other types of rollers commonly used in bearings, such as cylindrical rollers. Also, the bearing can be sealed, and a dielectric liquid is provided between the inner race and the outer race.

[0082] Accordingly, by the present disclosure, a plasma processing chamber is provided, including: a vacuum chamber; a substrate pedestal on a floor of the vacuum chamber; a dielectric window on an upper portion of the vacuum chamber; a coil disposed around the dielectric window, the coil connected to a rotatable shaft; a motor connected to the rotatable shaft; a radio frequency power source; and a non-contact coupler to capacitively couple radio frequency energy from the radio frequency power source to the coil. The dielectric window can form a ceiling of the vacuum chamber, and the coil can be above the ceiling. Further, the ceiling can form a flat disk, and the coil can include a plurality of excitation segments in a plane parallel to the ceiling. Alternatively, the ceiling can form a dome, and the coil can include a plurality of curved excitation segments. Further, the dielectric window can form a cylindrical extension of a sidewall of the vacuum chamber, and the coil can extend downward around the dielectric window.

[0083] The present disclosure includes a non-contact coupler including a capacitor having an input contact connected to a radio frequency power source and an output contact connected to a coil, and a dielectric spacer between the input contact and the output contact. In an embodiment, the input contact, the output contact, and the dielectric spacer include concentric rings. Embodiments include cases where the output contact is connected to or forms a portion of the rotatable shaft. Accordingly, the input contact is stationary, and the output contact rotates with the shaft. Further, the input contact, the output contact, and the dielectric spacer can form a rotational bearing to support the shaft. In an embodiment, the non-contact coupler includes a bearing having an electrically conductive inner race, an electrically conductive outer race, and a roller formed of a dielectric material.

[0084] In an embodiment, the plasma chamber includes a grounded coupler to couple the coil to a ground potential of the radio frequency power source. The grounded coupler can form a direct current break / radio frequency short. The coil can include a plurality of excitation segments connected in series or in parallel. The coil can include a plurality of straight excitation segments forming a plurality of rectangular coils. In an embodiment, at least two of the plurality of rectangular coils have different lengths. The motor can be directly connected to the rotatable shaft or connected to the rotatable shaft through a belt drive.

[0085] The present disclosure also includes a method of processing a substrate in a plasma chamber, including: inserting a substrate into the plasma chamber; injecting a process gas into the plasma chamber; activating a coil motor to rotate an induction coil; activating a radio frequency power source; capacitively coupling radio frequency energy from the radio frequency power source to the coil to ignite and sustain a plasma in the plasma chamber and process the substrate; when a processing time is complete, stopping the coupling of the radio frequency energy to the coil to extinguish the plasma; pumping any remaining exhaust gas from the plasma chamber; and removing the substrate from the plasma chamber.

[0086] It should be understood that the processes and techniques described herein are not inherently related to any particular apparatus and can be implemented by any suitable combination of components. Further, various types of general purpose devices can be used in accordance with the teachings described herein. The present application has been described in relation to particular examples, which are intended in all respects to be illustrative rather than restrictive. Those skilled in the art will appreciate that many different combinations will be suitable for practicing the present application.

[0087] Moreover, other implementations of the application will be apparent from consideration of the specification and the practice of the application disclosed herein. Various aspects and / or components of the described embodiments can be used singly or in any combination. The true scope and spirit of the application is defined by the following claims.

Claims

1. A plasma processing apparatus, comprising: a vacuum chamber; a susceptor located in the vacuum chamber for carrying a substrate during processing; a dielectric window located on top of the vacuum chamber opposite the susceptor; a coil located at least partially above the dielectric window, the coil comprising at least two elongated excitation segments; a radio frequency power source for supplying a radio frequency signal to the coil such that the current directions of the two excitation segments are in the same direction; a rotation drive device for driving the coil and / or the susceptor to rotate such that the coil and the susceptor are relatively rotatable during processing. The electromagnetic fields generated by the two excitation segments superimpose each other to generate an elongated electromagnetic field distribution above the substrate. The excitation segments of the coil are connected in series or in parallel. The two excitation segments are located parallel to each other. The length of the excitation segments is greater than the diameter of the substrate. The length of the excitation segments is greater than the diameter of the dielectric window. The coil comprises at least two excitation segments and a return segment connecting two adjacent excitation segments, the return segment and the excitation segments are located in different planes. The coil further comprises a height connecting segment connecting the excitation segments and the return segment, the height connecting segment makes the distance from the return segment to the dielectric window greater than the distance from the excitation segments to the dielectric window.

2. The plasma processing apparatus of claim 1, wherein, The length of the height connecting segment is greater than 1 / 2 of the length of the excitation segments.

3. The plasma processing apparatus of claim 1, wherein, The excitation segments comprise a center excitation segment and edge excitation segments located on both sides of the center excitation segment, the distance from the center excitation segment to the dielectric window is greater than the distance from the edge excitation segments to the dielectric window.

4. The plasma processing apparatus of claim 1, wherein, The return segment comprises a center return segment and edge return segments located on both sides of the center return segment, the distance from the center return segment to the dielectric window is less than the distance from the edge return segments to the dielectric window.

5. The plasma processing apparatus of claim 1, wherein, The radio frequency power source supplies the radio frequency signal to the coil through a non-contact coupler, the non-contact coupler comprises a transmitting end and a receiving end, the receiving end is electrically connected to the input end of the coil, and the transmitting end is electrically connected to the radio frequency power source.

6. The plasma processing apparatus of claim 1, wherein, The receiving end rotates synchronously with the coil, and the receiving end rotates relatively to the transmitting end.

7. The plasma processing apparatus of claim 1, wherein, At least one of the receiving end and the transmitting end is a loop conductor.

8. The plasma processing apparatus of claim 7, wherein, The radio frequency power source supplies the radio frequency signal to the coil through a brush.

9. The plasma processing apparatus of claim 8, wherein, The lengths of the excitation segments are equal or unequal.

10. The plasma processing apparatus of claim 1, wherein, The coil is connected to a rotating shaft, and the rotation drive device drives the rotating shaft to rotate the coil.

11. The plasma processing apparatus of claim 7, wherein, The rotation drive device is a motor.

12. The plasma processing apparatus of claim 1, wherein, The dielectric window is dome-shaped, and the excitation segments of the coil are curved segments.

13. The plasma processing apparatus of claim 12, wherein, The dielectric window is cylindrical.

14. The plasma processing apparatus of claim 13, wherein, ​ 15. The plasma processing apparatus of claim 1, wherein, ​ 16. The plasma processing apparatus of claim 1, wherein, ​ 17. The plasma processing apparatus of claim 1, wherein, ​ 18. The plasma processing apparatus of claim 1, wherein, ​ 19. The plasma processing apparatus of claim 1, wherein, ​ 20. The plasma processing apparatus of claim 1, wherein, ​

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