Patent Application
20240429065
The present disclosure relates to various embodiments of methods of manufacturing metal lines for semiconductor devices.
During the back-end-of-line (BEOL) process of manufacturing a semiconductor device, metal interconnect lines are formed in a variety of metal layers (e.g., metal layer M1, metal layer M2, etc.). In some related art semiconductor devices, the metal interconnect lines are formed of copper, which may be readily electroplated into the desired pattern. However, at smaller scales, such as below 15 nm width, the resistivity of copper increases due to photon scattering, which makes copper unsuitable for further semiconductor scaling.
Other related art semiconductor devices may utilize ruthenium to form the metal interconnect lines in the BEOL process. Unlike copper, ruthenium does not have increased resistivity at smaller scales. Ruthenium is typically etched into the desired pattern utilizing a photoresist or a hard mask. However, related art etching processes, such as O2 plasma etching of the ruthenium layer, results in the generation of volatile compounds, including ions and radials. Radicals are isotropic and result in the ruthenium layer being undercut underneath the photoresist or the hard mask during the related art O2 plasma etching task. Accordingly, these related art processes of etching ruthenium have insufficient fidelity (i.e., insufficient profile control), which may inhibit further scaling of semiconductor devices. For instance,
The above information disclosed in this Background section is only to enhance understanding of background information pertaining to the present disclosure and may contain information that does not constitute prior art.
The present disclosure relates to various embodiments of a method of manufacturing an interconnect in a metal layer in a semiconductor back-end-of-line process. In one embodiment, the method includes an N2 plasma task, through an opening in a hard mask, a ruthenium layer on a substrate including transistors. The N2 plasma passivation task forms a ruthenium nitride layer on the ruthenium layer, and the ruthenium nitride layer includes a first portion aligned with the opening and a second portion underneath the hard mask. The method also includes performing an H2 plasma reduction task on the ruthenium nitride layer after the N2 plasma passivation task. The H2 plasma reduction task removes the first portion of the ruthenium nitride layer. The method also includes O2 plasma etching the ruthenium layer after the H2 plasma reduction task, and repeatedly performing the N2 plasma passivation task, the H2 plasma reduction task, and the O2 plasma etching task to remove the ruthenium layer down to the substrate.
The method may also include performing a forming gas anneal.
The H2 plasma reduction task may include a mixture of H2 gas and a noble gas.
The noble gas may be argon (Ar).
A ratio of H2:Ar may be in a range from 1:2 to 4:1.
The N2 plasma passivation task may be performed with a radio frequency power in a range from approximately 300 to approximately 700 W, with a bias is in a range from approximately 8 W to approximately 12 W, with a pressure in a range from approximately 24 mTorr to approximately 36 mTorr, and for a duration of approximately 24 seconds to approximately 36 seconds.
The N2 plasma passivation task may be performed with a radio frequency power of approximately 500 W, a bias of approximately 10 W, a pressure of approximately 30 mTorr, and for a duration of approximately 30 seconds.
The H2 plasma reduction task may be performed with a radio frequency power in a range from approximately 300 W to approximately 700 W, a bias in a range from approximately 12 W to approximately 18 W, a pressure in a range from approximately 40 mTorr to approximately 60 mTorr, and for a duration of approximately 12 seconds to approximately 18 seconds.
The H2 plasma reduction task may be performed with a radio frequency power of approximately 500 W, a bias of approximately 15 W, a pressure of approximately 50 m Torr, and for a duration of approximately 15 seconds.
The H2 plasma reduction task may be performed for a duration that is approximately half of a duration of the N2 plasma passivation task and/or the O2 plasma etching task.
The H2 plasma reduction task may be performed at at least an approximately 50% higher pressure than the N2 plasma passivation task and/or the O2 plasma etching task.
The hard mask may include silicon dioxide (SiO2) or silicon nitride (SiNx).
A thickness of the ruthenium layer may be in a range from approximately 20 nm to approximately 400 nm.
The number of cycles may be in a range from 20 to 400.
The present disclosure also relates to a method including N2 plasma passivation, through an opening a hard mask, of a ruthenium layer. The N2 plasma passivation task forms a ruthenium nitride layer on the ruthenium layer. The ruthenium nitride layer includes a first portion aligned with the opening and a second portion underneath the hard mask. The method also includes H2 plasma reduction of the ruthenium nitride layer after the N2 plasma passivation task. The H2 plasma reduction task removes the first portion of the ruthenium nitride layer. The method further includes O2 plasma etching the ruthenium layer after the H2 plasma reduction task, and repeatedly performing the N2 plasma passivation task, the H2 plasma reduction task, and the O2 plasma etching task.
The H2 plasma reduction task may include a mixture of H2 gas and a noble gas.
The H2 plasma reduction task may be performed for a duration that is approximately half of a duration of the N2 plasma passivation task and/or the O2 plasma etching task.
The H2 plasma reduction task may be performed at at least an approximately 50% higher pressure than the N2 plasma passivation task and/or the O2 plasma etching task.
Following the O2 plasma etching, the ruthenium layer may have a substantially straight sidewall angle.
This summary is provided to introduce a selection of features and concepts of embodiments of the present disclosure that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter. One or more of the described features or tasks may be combined with one or more other described features or tasks to provide a workable method or system.
The features and advantages of embodiments of the present disclosure will be better understood by reference to the following detailed description when considered in conjunction with the drawings. The drawings are not necessarily drawn to scale.
The present disclosure relates to various embodiments of a method of forming ruthenium metal lines in the back-end-of-line (BEOL) of a semiconductor device, such as the metal lines in the M1 metal layer and/or the M2 metal layer of the BEOL. In one or more embodiments, the method includes iteratively performing an N2 plasma passivation task, an H2 plasma reduction task, and an O2 plasma etching task of a ruthenium layer through a patterned hard mask. The N2 plasma passivation task forms an RuNx diffusion barrier along the sidewall of the ruthenium layer that is configured to prevent the O2 plasma etching task from undercutting the ruthenium underneath the hard mask. The H2 plasma reduction task is configured to selectively remove a portion of the RuNx diffusion barrier in the openings of the hard mask and leave the portion of the RuNx diffusion barrier underneath the hard mask (i.e., along the sidewalls of the ruthenium layer). Additionally, in one or more embodiments, the H2 plasma reduction task may include a noble gas, such as argon, which shifts the electron temperature distribution and is thereby configured to prevent (or at least mitigate against) the H2 plasma reduction task excessively etching the hard mask (e.g., rounding the upper corners of the hard mask). Otherwise, excessive rounding of the corners of the hard mask during the H2 plasma reduction task might scatter ions that impact the rounded corners of the hard mask and these scattered ions may undercut the ruthenium layer.
In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. It will be understood, however, by those skilled in the art that the disclosed aspects may be practiced without these specific details. In other instances, well-known methods, procedures, components and circuits have not been described in detail to not obscure the subject matter disclosed herein.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment disclosed herein. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” or “according to one embodiment” (or other phrases having similar import) in various places throughout this specification may not necessarily all be referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In this regard, as used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not to be construed as necessarily preferred or advantageous over other embodiments. Additionally, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Also, depending on the context of discussion herein, a singular term may include the corresponding plural forms and a plural term may include the corresponding singular form. Similarly, a hyphenated term (e.g., “two-dimensional,” “pre-determined,” “pixel-specific,” etc.) may be occasionally interchangeably used with a corresponding non-hyphenated version (e.g., “two dimensional,” “predetermined,” “pixel specific,” etc.), and a capitalized entry (e.g., “Counter Clock,” “Row Select,” “PIXOUT,” etc.) may be interchangeably used with a corresponding non-capitalized version (e.g., “counter clock,” “row select,” “pixout,” etc.). Such occasional interchangeable uses shall not be considered inconsistent with each other.
Also, depending on the context of discussion herein, a singular term may include the corresponding plural forms and a plural term may include the corresponding singular form. It is further noted that various figures (including component diagrams) shown and discussed herein are for illustrative purpose only, and are not drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.
The terminology used herein is for the purpose of describing some example embodiments only and is not intended to be limiting of the claimed subject matter. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood that when an element or layer is referred to as being on, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
The terms “first,” “second,” etc., as used herein, are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.) unless explicitly defined as such. Furthermore, the same reference numerals may be used across two or more figures to refer to parts, components, blocks, circuits, units, or modules having the same or similar functionality. Such usage is, however, for simplicity of illustration and ease of discussion only; it does not imply that the construction or architectural details of such components or units are the same across all embodiments or such commonly-referenced parts/modules are the only way to implement some of the example embodiments disclosed herein.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the term “module” refers to any combination of software, firmware and/or hardware configured to provide the functionality described herein in connection with a module. For example, software may be embodied as a software package, code and/or instruction set or instructions, and the term “hardware,” as used in any implementation described herein, may include, for example, singly or in any combination, an assembly, hardwired circuitry, programmable circuitry, state machine circuitry, and/or firmware that stores instructions executed by programmable circuitry. The modules may, collectively or individually, be embodied as circuitry that forms part of a larger system, for example, but not limited to, an integrated circuit (IC), system on-a-chip (SoC), an assembly, and so forth.
As illustrated in
In one or more embodiments, the task 210 of N2 plasma passivation may be performed with a radio frequency (RF) power in a range from approximately 300 watts (W) to approximately 700 W, a bias in a range from approximately 8 W to approximately 12 W, a pressure in a range from approximately 24 millitorr (mTorr) to approximately 36 mTorr, and for a duration of approximately 24 seconds to approximately 36 seconds. In one embodiment, the task 210 of N2 plasma passivation may be performed with an RF power of approximately 500 W, a bias of approximately 10 W, a pressure of approximately 30 m Torr, and for a duration of approximately 30 seconds.
With reference now to
In one or more embodiments, the H2 plasma reduction task 220 may include a mixture of H2 and a noble gas (e.g., the H2 gas may be mixed with argon (Ar), helium (He), krypton (Kr), neon (Ne), xenon (Xe), and/or radon (Rn)). The addition of a noble gas is configured to shift the electron temperature distribution and thereby reduce the number of H2 ions striking the hard mask 303, which might otherwise cause the sidewall of the hard mask 303 to become rounded (e.g., the addition of the noble gas is configured to minimize or at least reduce the rounding of the upper corners 308 of the hard mask 303 adjacent to the opening 302, which have the highest flux). In this manner, including a noble gas in the H2 plasma reduction task 220 is configured to reduce the rounding of the sidewall of the hard mask 303 compared to an embodiment in which the H2 plasma reduction task 220 is performed with H2 only. As described in more detail below, the rounding of the sidewall of the hard mask 303 might otherwise cause the scattering of ions that may undercut the ruthenium layer 301 during a subsequent task of the method 200. In one or more embodiments, the ratio of H2 and Ar (i.e., H2:Ar) in the task 220 may be in a range from approximately 1:2 to approximately 4:1. For instance, in one or more embodiments, the task 220 of plasma reduction may utilize a H2:Ar 1:2 mixture, a H2:Ar 1:1 mixture, a H2:Ar 2:1 mixture, or a H2:Ar 4:1 mixture.
In one or more embodiments, the task 210 of H2 plasma passivation (utilizing H2 or H2 and a noble gas, such as argon) may be performed with an RF power in a range from approximately 300 W to approximately 700 W, a bias in a range from approximately 12 W to approximately 18 W, a pressure in a range from approximately 40 mTorr to approximately 60 m Torr, and for a duration of approximately 12 seconds to approximately 18 seconds. In one embodiment, the task 220 of H2 plasma reduction (utilizing H2 or H2 and a noble gas, such as argon) may be performed with an RF power of approximately 500 W, a bias of approximately 15 W, a pressure of approximately 50 mTorr, and for a duration of approximately 15 seconds.
With reference now to
In one or more embodiments, the task 210 of N2 plasma passivation, the task 220 of H2 (or H2+Ar) plasma reduction, and the task 230 of O2 etching are repeatedly performed. In one or more embodiments, the plasma tasks 210, 220, and 230 may each be repeatedly performed in that order a number of times in a range from 5 to 40. The number of repetitions may depend, for example, on the conditions (e.g., the RF power, the pressure, and the duration) of the plasma tasks 210, 220, 230.
In one or more embodiments, one or more parameters of the H2 plasma reduction task 220 may be selected to minimize or at least reduce the degradation of the hard mask 303 and thereby increase the fidelity and profile control of the method 200. Otherwise, the method 200 may result in undesirable rounding of the sidewall corners 308 of the hard mask 303. In one or more embodiments, the task 220 of H2 plasma reduction (or H2 and a noble gas plasma etching) may be performed for a duration that is approximately half of the duration of the task 210 of the N2 plasma passivation and/or the task 230 of the O2 plasma etching. In one or more embodiments, the task 220 of H2 plasma reduction (or H2 and the noble plasma etching) may be performed at a higher pressure (e.g., an approximately 50% higher pressure or an approximately 60% higher pressure or more) than the task 210 of N2 plasma passivation and/or the task 230 of the O2 plasma etching. Lowering the exposure time and decreasing the electron temperature by reducing the RF power and increasing the pressure of the H2 plasma reduction task 220 is configured to reduce the degradation of the sidewalls of the hard mask 303, and thereby reduce the undercut of the ruthenium layer 201.
In one or more embodiments, the parameters of the N2 plasma passivation task 210, the H2 plasma reduction task 220, and the O2 plasma etching task 230 (e.g., radio frequency power, bias power, pressure, and/or process duration) may vary depending, for example, on the size of the reactor utilized.
With reference now to
With reference now to
The above-described tasks 210, 220, and 230 of etching the ruthenium layer to form a metal interconnect in one of the metal layers (e.g., lines and/or vias in metal layer M1 and/or metal layer M2) during the BEOL process may be repeated to form metal interconnects (lines and/or vias) in other layers of a semiconductor device. Additionally, above-described tasks 210, 220, and 230 of etching the ruthenium layer may be performed to form a ruthenium structure in any other suitable application or device. Furthermore, in one or more embodiments, the above-described tasks 210, 220, and 230 of etching the ruthenium layer are configured to form an opening in the ruthenium layer that has a straight (or substantially straight) sidewall angle (i.e., a non-tapered opening), unlike related art O2 plasma etching methods that form an opening in the ruthenium layer that has a tapered sidewall angle (i.e., an opening that is wider at the top and narrower at the bottom). In one or more embodiments, the above-described tasks 210, 220, and 230 are also configured to etch a ruthenium layer without “loading effects” (or at least mitigating against “loading effects”) such that both large and small ruthenium features are etched to the same (or substantially the same) depth, unlike related art O2 plasma etching methods in which larger ruthenium features are etched deeper than smaller ruthenium features.
While this specification may contain many specific implementation details, the implementation details should not be construed as limitations on the scope of any claimed subject matter, but rather be construed as descriptions of features specific to particular embodiments. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.
Thus, particular embodiments of the subject matter have been described herein. Other embodiments are within the scope of the following claims. In some cases, the actions set forth in the claims may be performed in a different order and still achieve desirable results. Additionally, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.
As will be recognized by those skilled in the art, the innovative concepts described herein may be modified and varied over a wide range of applications. Accordingly, the scope of claimed subject matter should not be limited to any of the specific exemplary teachings discussed above, but is instead defined by the following claims.
The present application claims priority to and the benefit of U.S. Provisional Application No. 63/522,620, filed Jun. 22, 2023, the entire content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63522620 | Jun 2023 | US |
