Patent Application
20210391154
The present disclosure relates generally to the field of semiconductor manufacturing apparatuses and particularly to an anisotropic etch apparatus with local etch direction adjustment capability and methods for operating the same.
During a reactive ion etch process, ions accelerated along the direction of local electric field and impinges on an etch target, such as a semiconductor substrate with a patterned etch mask layer thereupon. In order to form etch patterns extending perpendicular to the top surface of the substrate, the electric field lines need to be perpendicular to the top surface of the semiconductor substrate. This is mostly the case in the middle portion of the semiconductor substrate. However, the contour of electric field lines overlying edge portions of the semiconductor substrate is affected by the local geometry of conductive components of the reactive ion etch apparatus, such as the edge ring. Thus, etch direction on edge dies on the semiconductor substrate can have significant tilt from the vertical direction, and can adversely impact the yield of semiconductor dies on the semiconductor substrate.
According to an aspect of the present disclosure, an anisotropic etch apparatus contains an electrostatic chuck located in a vacuum enclosure and including a lower electrode therein, a plurality of conductive outer edge ring segments surrounding the electrostatic chuck and configured for independent vertical movement relative to the electrostatic chuck, an upper electrode overlying the lower electrode and located in the vacuum enclosure, and a main radio frequency (RF) power source configured to provide radio frequency bias voltage between the lower electrode and the upper electrode.
According to another embodiment an anisotropic etch apparatus contains an electrostatic chuck located in a vacuum enclosure and including a lower electrode therein, an upper electrode overlying the lower electrode and located in the vacuum enclosure, a main radio frequency (RF) power source configured to provide radio frequency bias voltage between the lower electrode and the upper electrode, a plurality of electrically isolated, conductive edge ring segments surrounding the electrostatic chuck, and a plurality of auxiliary RF power sources, each of which is configured to independently provide a different auxiliary RF bias voltage to one of the conductive edge ring segments.
As discussed above, the present disclosure is directed to an anisotropic etch apparatus with local etch direction adjustment capability and methods for operating the same, the various aspects of which are described herebelow in detail.
The drawings are not drawn to scale. Multiple instances of an element may be duplicated where a single instance of the element is illustrated, unless absence of duplication of elements is expressly described or clearly indicated otherwise. Ordinals such as “first,” “second,” and “third” are employed merely to identify similar elements, and different ordinals may be employed across the specification and the claims of the instant disclosure. The term “at least one” element refers to all possibilities including the possibility of a single element and the possibility of multiple elements.
The same reference numerals refer to the same element or similar element. Unless otherwise indicated, elements having the same reference numerals are presumed to have the same composition and the same function. Unless otherwise indicated, a “contact” between elements refers to a direct contact between elements that provides an edge or a surface shared by the elements. If two or more elements are not in direct contact with each other or among one another, the two elements are “disjoined from” each other or “disjoined among” one another. As used herein, a first element located “on” a second element can be located on the exterior side of a surface of the second element or on the interior side of the second element. As used herein, a first element is located “directly on” a second element if there exist a physical contact between a surface of the first element and a surface of the second element. As used herein, a first element is “electrically connected to” a second element if there exists a conductive path consisting of at least one conductive material between the first element and the second element. As used herein, a “prototype” structure or an “in-process” structure refers to a transient structure that is subsequently modified in the shape or composition of at least one component therein.
As used herein, a “layer” refers to a material portion including a region having a thickness. A layer may extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer may be a region of a homogeneous or inhomogeneous continuous structure that has a thickness less than the thickness of the continuous structure. For example, a layer may be located between any pair of horizontal planes between, or at, a top surface and a bottom surface of the continuous structure. A layer may extend horizontally, vertically, and/or along a tapered surface. A substrate may be a layer, may include one or more layers therein, or may have one or more layer thereupon, thereabove, and/or therebelow.
As used herein, a first surface and a second surface are “vertically coincident” with each other if the second surface overlies or underlies the first surface and there exists a vertical plane or a substantially vertical plane that includes the first surface and the second surface. A substantially vertical plane is a plane that extends straight along a direction that deviates from a vertical direction by an angle less than 5 degrees. A vertical plane or a substantially vertical plane is straight along a vertical direction or a substantially vertical direction, and may, or may not, include a curvature along a direction that is perpendicular to the vertical direction or the substantially vertical direction.
Referring to
A gas supply manifold 113 configured to provide influx of at least one process gas into the vacuum enclosure 110 may be provided in the exemplary anisotropic etch apparatus 100. The at least one process gas may include any process gas that can be employed for any known anisotropic etch process in the art. For example, the at least one process gas can include at least one gas phase etchant (e.g., a fluorine and/or a chlorine containing gas), and may also include an oxidant, a reducing agent, and/or a carrier gas (e.g., hydrogen or argon). The gas supply manifold 113 may be configured to provide influx of the at least one process gas through a sidewall of the vacuum enclosure 110 located on an opposite side of the pumping port 111. Optionally, the gas supply manifold may be configured to provide a purge gas and/or a backfill gas.
An electrostatic chuck 220 is located within the vacuum enclosure 110. The electrostatic chuck 220 includes a dielectric matrix having a planar top surface on which a substrate 10 (such as a semiconductor wafer) can be disposed. The electrostatic chuck 220 includes a lower electrode 112. The lower electrode 112 can have a uniform thickness, and can include a conductive material, such as a metallic material. The lower electrode 112 may be encased within a dielectric matrix material of the electrostatic chuck 220, which may include a ceramic material, quartz, aluminum oxide, or any other suitable dielectric material that can provide mechanical strength and can withstand the elevated temperature during a deposition process.
In one embodiment, the electrostatic chuck 220 has a circular horizontal cross-sectional shape, the lower electrode 112 can have a circular horizontal cross-sectional shape with a smaller diameter than the circular horizontal cross-sectional shape of the electrostatic chuck 220. In one embodiment, electrostatic chuck 220 may have an axial symmetry around a vertical axis VA passing through the geometrical center of the electrostatic chuck 220.
An upper electrode 160 is located over the electrostatic chuck 220. The lower electrode 112 and the upper electrode 160 can be connected to output nodes of at least one primary radio frequency (RF) power source 180. The at least one primary RF power source 180 can be configured to provide a radio frequency bias voltage between the lower electrode 112 and the upper electrode 160. The lower electrode 112 and the upper electrode 160 may be powered by a common RF power source 180, or may be powered by two separate primary RF power sources that can independently control the power transmitted through the lower electrode 112 and the upper electrode 160.
According to an aspect of the present disclosure, a plurality of conductive outer edge ring segments 144 are provided, which are configured for independent vertical movement relative to the electrostatic chuck 220. The plurality of conductive outer edge ring segments 144 collectively function as a component of an edge ring that contacts a substrate 10 that is disposed on the electrostatic chuck 220. The plurality of conductive outer edge ring segments 144 laterally surround the electrostatic chuck 220.
In one embodiment, an annular conductive edge ring 142 may be provided around an upper periphery of the electrostatic chuck 220. The annular conductive edge ring 142 can laterally surround the electrostatic chuck 220, and may be concentric with the electrostatic chuck 220. The annular conductive edge ring 142 may have a top surface that is flush with the top surface of the electrostatic chuck 220. A cylindrical inner sidewall of the annular conductive edge ring 142 can contact a sidewall of the electrostatic chuck 220. The annular conductive edge ring 142 can be affixed to the electrostatic chuck 220 by tight fit and/or by at least one fixture element such as a screw, clamp and/or a pin. In one embodiment, the annular conductive edge ring 142 can be configured to contact a bottom surface of a substrate 10 that is disposed on top of the electrostatic chuck 220.
The plurality of conductive outer edge ring segments 144 can be electrically connected to the annular conductive edge ring 142. For example, the plurality of conductive outer edge ring segments 144 can contact a respective portion of a cylindrical outer sidewall of the annular conductive edge ring 142. In this case, each of the plurality of conductive outer edge ring segments 144 can be electrically connected to the substrate 10 through the annular conductive edge ring 142. In one embodiment, each of the plurality of conductive outer edge ring segments 144 can comprise a respective inner sidewall that contacts a respective portion of a cylindrical outer sidewall of the annular conductive edge ring 142.
In one embodiment, each inner sidewall of the plurality of conductive outer edge ring segments 144 can be vertical, and can have a concave profile in a horizontal cross-sectional view. Such an inner sidewall is herein referred to as a concave vertical sidewall. The cylindrical outer sidewall of the annular conductive edge ring 142 can be a convex vertical sidewall, i.e., a sidewall having a vertical profile (i.e., without any tilt angle with respect to the vertical direction) in a vertical cross-sectional view and having a convex profile in a horizontal cross-sectional view.
The plurality of conductive outer edge ring segments 144 can have the same size, and can laterally extend by a same azimuthal angle around the vertical axis VA passing through the geometrical center of the electrostatic chuck 220. The total number of conductive outer edge ring segments 144 can be N, which is an integer greater than 2, i.e., an integer such as 3, 4, 5, 6, 7, 8, etc. In this case, each of the conductive outer edge ring segments 144 can azimuthally extend around the vertical axis VA passing through the geometrical center of the electrostatic chuck 220 by an azimuthal angle range of 2π/N.
In one embodiment, the plurality of conductive outer edge ring segments 144 comprises N conductive outer edge ring segments 144, in which N is in a range from 3 to 60. Each of the conductive outer edge ring segments 144 can be numerically numbered employing integers beginning with 1. Thus, if N conductive outer edge ring segments 144 are provided, the N conductive outer edge ring segments 144 can include a first conductive outer edge ring segment 144_1, a second conductive outer edge ring segment 144_2, a third conductive outer edge ring segment 144_3, and so on up to the N-th conductive outer edge ring segment 144_N. An i-th conductive outer edge ring segment 144_i can be located between an (i−1)-th conductive outer edge ring segment 144_(i−1) and an (i+1)-th conductive outer edge ring segment 144_(i+1) for all i other than 1 and N. In one embodiment, each of the plurality of conductive outer edge ring segments 144 can have an azimuthal extent in a range from π/30 radian to 2π/3 radian. In one embodiment, the N conductive outer edge ring segments 144 can be arranged with an N-fold rotational symmetry around the vertical axis VA passing through the geometrical center of the electrostatic chuck 220 in a plan view, i.e., a view along a downward vertical direction.
In one embodiment, each of the plurality of conductive outer edge ring segments 144 can comprise a tapered top surface having a height that increases with a radial distance from the vertical axis VA passing through the geometrical center of the electrostatic chuck 220. The tapered top surface of the conductive outer edge ring segments 144 has the effect of gradually changing the equipotential line, which extends across all surfaces of the plurality of conductive outer edge ring segments 144, all surfaces of the annular conductive edge ring 142, and the surfaces of the substrate 10 (unless charge accumulation occurs within the substrate 10 during an anisotropic etch process). According to an aspect of the present disclosure, the height of the conductive outer edge ring segments 144 can be independently adjusted before, during, and/or after an anisotropic etch process to change the contour of the equipotential line. Changing the contour of the equipotential line around the periphery of a substrate 10 has the effect of tilting the impingement direction of charged ions during the anisotropic etch process, and thus, causes a change in the tilt angle of trenches or openings formed within films (e.g., insulating, semiconductor and/or conductive layers) located over the top surface of the substrate 10.
According to an embodiment of the present disclosure, a plurality of height adjustment assemblies 148 can be provided. For example, a separate height adjustment assembly 148 can be provided for each conductive outer edge ring segment 144. Each height adjustment assembly 148 can be configured to independently elevate or lower a respective one of the plurality of conductive outer edge ring segments 144. Generally, each of the plurality height adjustment assemblies 148 comprises an actuator 147 located within the vacuum enclosure 110 or outside the vacuum enclosure 110 and configured to actuate vertical movement of a respective height adjustment assembly 148.
Further, each of the plurality height adjustment assemblies 148 comprises moving parts (145, 146) that are actuated and move in a linear motion or in a rotational motion. Any combination of moving parts (145, 146) that can vertically move the ring segments 144 may be employed for the height adjustment assemblies 148. Examples of moving parts (145, 146) that may be employed for the respective height adjustment assemblies 148 include, but are not limited to, racks and pinions, worm gears (e.g., worm drive), bevel gears, and/or any other mechanical part that may produce a vertical linear motion.
The actuators 147 may be motorized, or may be configured to be manually adjusted. In case the actuators 147 are motorized, a differential height controller 140 may be provided to enable individual adjustment of the height of the conductive outer edge ring segments 144 without opening the vacuum enclosure 110. The differential height controller 140 can be configured to independently actuate each of the actuators 147 for the plurality of height adjustment assemblies 148 via a wired or wireless data connection. In case the actuators 147 are not motorized, each of the plurality height adjustment assemblies 148 can be configured to mechanically actuate a respective one of the plurality of conductive outer edge ring segments 144 upon application of physical force thereto.
In one embodiment, the annular conductive edge ring 142 comprises a laterally-protruding flange portion including holes, and each height adjustment assembly 148 comprises a component (e.g., worm gear or rack gear) that vertically extends through a respective hole in the laterally-protruding flange portion of the annular conductive edge ring 142. In one embodiment, each of the plurality of conductive outer edge ring segments 144 may be configured to vertically move by at least 1 mm, such as from 1 mm to 10 mm.
A volume between the electrostatic chuck 220 and the upper electrode 160 comprises a plasma zone 150. The plurality of conductive outer edge ring segments 144 can be arranged along a periphery of the plasma zone 150 to affect the equipotential line around the periphery of the plasma zone 150 during the anisotropic etch process. Thus, independent adjustment of the height of the conductive outer edge ring segments 144 around the electrostatic chuck 220 can result in azimuthally independent adjustment of etch direction along the periphery of the substrate 10.
In one embodiment, the electrostatic chuck 220 and the upper electrode 160 are vertically spaced from each other by a uniform spacing, and at least two of the plurality of conductive outer edge ring segments 144 can be vertically spaced from the upper electrode 160 by different vertical spacings from each other.
In one embodiment the edge ring 142 and the conductive outer edge ring segments 144 may be electrically connected to at least one optional auxiliary RF power source 190 in addition to the at least one primary RF power source 180. In the first embodiment shown in
In second embodiment shown in
Each of the conductive inner edge ring segments can be numerically numbered employing integers beginning with 1. Thus, if N conductive inner edge ring segments are provided, the N conductive inner edge ring segments can include a first conductive inner edge ring segment 242_1, a second conductive inner edge ring segment 242_2, a third conductive inner edge ring segment 242_3, and so on up to the N-th conductive inner edge ring segment 242_N. An i-th conductive inner edge ring segment 242 can be located between an (i−1)-th conductive inner edge ring segment 144_(i−1) and an (i+1)-th conductive inner edge ring segment 144_(i+1) for all i other than 1 and N. In one embodiment, each of the plurality of conductive inner edge ring segments 242 can have an azimuthal extent in a range from π/30 radian to 2π/3 radian. In one embodiment, the N conductive inner edge ring segments 242 can be arranged with an N-fold rotational symmetry around the vertical axis VA passing through the geometrical center of the electrostatic chuck 220 in a plan view, i.e., a view along a downward vertical direction. In one embodiment, each of the N conductive inner edge ring segments 242 can be electrically connected to a respective one of the N conductive outer edge ring segments 144.
In the second embodiment, each of the combination ring segments (242, 144) containing one conductive inner edge ring segment 242 which is electrically connected to a respective one conductive outer edge ring segment 144 is electrically connected to a different auxiliary RF power source 190. There may be N auxiliary RF power sources 190 (i.e., 190_1, 190_2, 190_3, . . . 190_i, . . . 190_N), each electrically connected to one of the N combination ring segments (242, 144). Each of the auxiliary power sources may apply different RF bias voltage to different combination ring segment (242, 144). In the second embodiment of the present disclosure, each outer edge ring segment 144 may be raised and lowered independently from the other outer edge ring segments 144.
Referring to
In this case, the tilt in the trenches 49 through the at least one material layer 20 can be reduced or eliminated by raising the conductive outer edge ring segment 144_i, for example, by actuating the corresponding actuator 147, without necessarily raising or lowering the other outer edge ring segments 144 to remedy the asymmetric tilt of the edge ring.
Referring to
Referring to the second embodiment shown in
Referring to the third embodiment shown in
Referring to all drawings and according to various embodiments of the present disclosure, a method of operating an anisotropic etch apparatus 100 of the present disclosure is provided. A substrate 10 can be loaded on a top surface of the electrostatic chuck 220, and portions of the substrate 10 can be anisotropically etched employing a reactive ion etch process.
In one embodiment, the method further comprises vertically moving a first one of the conductive outer edge ring segments 144 without moving a second one of the conductive outer edge ring segments 144. In one embodiment, the method further comprises applying a first auxiliary RF bias voltage to the first one of the conductive outer edge ring segments and applying a second auxiliary RF bias voltage different from the first auxiliary bias voltage to the second one of the conductive outer edge ring segments.
In one embodiment, a patterned etch mask layer 21 can be formed over a front surface of the substrate 10 prior to loading the substrate 10 on the top surface of the electrostatic chuck 220. The portions of the substrate 10 (e.g., layers located over the substrate) that are anisotropically etched comprise portions of the substrate 10 that are not masked by the patterned etch mask layer 21.
Adjustment of the ion impingement direction IID may be based on measurement of etch directions on a previously processed substrate 10. For example, the substrate 10 can be unloaded after the reactive ion etch process, and the tilt angle of etch patterns can be measured at a peripheral region of the substrate 10. The height of at least one of the plurality of conductive outer edge ring segments 144 located at a position corresponding to a non-zero tilt angle in the etch patterns can be subsequently adjusted and/or an auxiliary RF bias voltage may be adjusted so that the next substrate can be processed with reduced tilt angles throughout all azimuthal angle ranges.
In one embodiment, the anisotropic etch apparatus 100 can comprise a plurality of height adjustment assemblies 148 configured to independently elevate or lower a respective one of the plurality of conductive outer edge ring segments 144. Each of the plurality height adjustment assemblies 148 can comprise an actuator 147 located within the vacuum enclosure 110 or outside the vacuum enclosure 110 and configured to actuate vertical movement of a conductive outer edge ring segment 144. The height of at least one of the plurality of conductive outer edge ring segments 144 can be adjusted by actuating at least one actuator 147 connected to at least one of the plurality of conductive outer edge ring segments 144.
The various embodiments of the present disclosure can be employed to reduce or eliminate asymmetric tilt of the edge ring to provide a substantially vertical ion impingement directions IID across the entire periphery of a substrate 10 irrespective of any disturbances to the equipotential line EPL due to any nonuniformity in the surface conditions and/or geometrical conditions in the anisotropic etch apparatus 100. Trenches and via openings through material layers on a substrate can be formed with a more uniform vertical profile employing the anisotropic etch apparatus 100 of the present disclosure.
Although the foregoing refers to particular preferred embodiments, it will be understood that the disclosure is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the disclosure. Compatibility is presumed among all embodiments that are not alternatives of one another. The word “comprise” or “include” contemplates all embodiments in which the word “consist essentially of” or the word “consists of” replaces the word “comprise” or “include,” unless explicitly stated otherwise. Where an embodiment employing a particular structure and/or configuration is illustrated in the present disclosure, it is understood that the present disclosure may be practiced with any other compatible structures and/or configurations that are functionally equivalent provided that such substitutions are not explicitly forbidden or otherwise known to be impossible to one of ordinary skill in the art. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety.
