Patent Application
20250201552
The present invention relates generally to the electrical, electronic and computer arts and, more particularly, to deposition techniques for semiconductor fabrication and the like.
Area selective deposition (ASD) is a technique for material deposition where material is deposited only on desired areas of a substrate. In a prior art approach, inhibitors are employed to achieve ASD on metal-dielectric patterns. These techniques begin with a structure including a dielectric, such as SiCOH ultra-low-K dielectric, with copper lines located between dielectric regions. An inhibitor is deposited, which selectively attaches to the copper. Then, additional dielectric is deposited. The additional dielectric adheres everywhere except where the inhibitor is located. When the inhibitor is removed, a structure is obtained including a dielectric, such as SiCOH ultra-low-K dielectric, with copper lines located between dielectric regions, and with the deposited additional dielectric over the dielectric from the original structure, but not over the copper. This structure can be obtained without having to use traditional lithography processes.
Principles of the invention provide techniques for electromagnetic wave assisted area selective deposition. In one aspect, an exemplary method includes providing an initial structure, which includes a substrate; a plurality of spaced-apart metal lines, outward of the substrate; and a plurality of dielectric regions, outward of the substrate, and between the plurality of spaced-apart metal lines. A further step includes applying a reactive material of interest on an outer surface of the initial structure to produce a secondary structure. A still further step includes applying electromagnetic radiation to the secondary structure to cause development of an electric field adjacent the plurality of dielectric regions, but not adjacent the plurality of spaced-apart metal lines. This in turn causes reaction of the reactive material of interest adjacent the plurality of dielectric regions, but not adjacent the plurality of spaced-apart metal lines, to produce a tertiary structure with unreacted reactive material of interest adjacent the plurality of spaced-apart metal lines and reacted reactive material of interest adjacent the plurality of dielectric regions.
In another aspect, another exemplary method includes providing an initial structure, which includes a substrate; a plurality of spaced-apart metal lines, outward of the substrate; and a plurality of dielectric regions, outward of the substrate, and between the plurality of spaced-apart metal lines. A further step includes carrying out a vapor deposition process while applying electromagnetic radiation to the initial structure to cause an electric field adjacent the plurality of dielectric regions, but not adjacent the plurality of spaced-apart metal lines, so that a vapor phase precursor forms a film adjacent the plurality of dielectric regions, but not adjacent the plurality of spaced-apart metal lines.
In still a further aspect, an exemplary apparatus includes a vacuum chamber; a workpiece holder disposed within the vacuum chamber; a precursor source disposed in communication with the vacuum chamber; and an electromagnetic wave source disposed in relation to the vapor chamber to irradiate a workpiece held in the workpiece holder while the precursor source is active.
As used herein, “facilitating” an action includes performing the action, making the action easier, helping to carry the action out, or causing the action to be performed. Thus, by way of example and not limitation, instructions executing on a processor might facilitate an action carried out by semiconductor fabrication equipment, by sending appropriate data or commands to cause or aid the action to be performed. Where an actor facilitates an action by other than performing the action, the action is nevertheless performed by some entity or combination of entities.
Techniques as disclosed herein can provide substantial beneficial technical effects, as will be discussed further below. Features and advantages will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
The following drawings are presented by way of example only and without limitation, wherein like reference numerals (when used) indicate corresponding elements throughout the several views, and wherein:
It is to be appreciated that elements in the figures are illustrated for simplicity and clarity. Common but well-understood elements that may be useful or necessary in a commercially feasible embodiment may not be shown in order to facilitate a less hindered view of the illustrated embodiments.
Principles of inventions described herein will be in the context of illustrative embodiments. Moreover, it will become apparent to those skilled in the art given the teachings herein that numerous modifications can be made to the embodiments shown that are within the scope of the claims. That is, no limitations with respect to the embodiments shown and described herein are intended or should be inferred.
Given the discussion herein (reference characters refer to the drawings discussed below), and referring to
In some cases, applying the electromagnetic radiation includes applying microwaves. This provides the benefit of selective deposition using microwave sources.
In one or more embodiments, applying the electromagnetic radiation includes carrying out at least one of controlling radiation intensity and controlling radiation duration so that an average bulk temperature of the secondary structure and an average bulk temperature of the tertiary structure do not exceed 500° C., or even 275° C., or even 150° C. This provides the benefit of near-instantaneous process employing electromagnetic wave durations on the nanosecond (ns) to second(s) scale.
One or more embodiments further include carrying out a finite element analysis to determine at least one of the radiation intensity and the radiation duration; the applying of the electromagnetic radiation is then carried out in accordance with the finite element analysis. This provides the benefit of adapting known finite element techniques to accurately predict intensity and/or duration.
One or more embodiments further include treating the tertiary structure to remove the unreacted reactive material of interest. The reactive material of interest can be, for example, photoresist and the treating can be, for example, developing and rinsing. This provides the benefit of enabling further processing.
Applying the electromagnetic radiation can include carrying out the at least one of the controlling of the radiation intensity and the controlling of the radiation duration so that a local temperature of the photoresist does not exceed its glass transition temperature. This provides the benefit of protecting the photoresist.
In some instances, as depicted, the photoresist is negative tone photoresist; however, other embodiments can employ positive tone photoresist. This provides the benefit of processing using commonly available photoresists.
Furthermore, given the discussion thus far, referring to
In one or more embodiments, applying the electromagnetic radiation includes applying microwaves. This provides the benefit of selective deposition using microwave sources.
Applying the electromagnetic radiation can include carrying out at least one of controlling radiation intensity and controlling radiation duration so that an average bulk temperature of the initial structure does not exceed 500° C., or even 275° C., or even 150° C. This provides the benefit of near-instantaneous process employing electromagnetic wave durations on the nanosecond (ns) to second(s) scale.
One or more embodiments further include carrying out a finite element analysis to determine at least one of the radiation intensity and the radiation duration; the applying of the electromagnetic radiation is then carried out in accordance with the finite element analysis. This provides the benefit of adapting known finite element techniques to accurately predict intensity and/or duration.
The vapor deposition process can be ALD or CVD, for example. The skilled artisan will appreciate that ALD precursors are known to be quite polar and will respond to the electric field. The described structure is introduced into the tool chamber in one or more embodiments. This provides the benefit of modifying known tools in accordance with aspects of the invention to carry out selective deposition.
For one or more embodiments, including both
Even further, given the discussion thus far, referring to
Techniques as disclosed herein can provide substantial beneficial technical effects. Some embodiments may not have these potential advantages and these potential advantages are not necessarily required of all embodiments. By way of example only and without limitation, one or more embodiments may provide one or more of:
Ability to deposit 1-100 nm thick, self-aligned material of interest (MOI) in a selective manner
A near-instantaneous process employing electromagnetic wave durations on the nanosecond (ns) to second(s) scale A one-step, direct-writing, area selective deposition approach on metal-dielectric patterns.
One or more embodiments provide area selective deposition techniques that do not need an inhibitor. We have found that application of electromagnetic waves (microwaves are a non-limiting example) to a metal-dielectric pattern will readily create a localized undulating electric field/energy profile inside and outside the pattern. In particular, the electric field inside the metal is zero (by definition), and consequently, the electric field is concentrated in the material that is in between the metal lines (i.e., in the dielectric, as well as the region atop the dielectric). A strong enough electric field can subsequently trigger chemical reaction/material transformation in a localized manner. This can be implemented in many different ways; two non-limiting examples of process flow are set forth below.
Microwaves include electromagnetic energy at the lower frequency end of the electromagnetic spectrum (0.3-300 GHz), and are a non-limiting example of electromagnetic waves. Within this region, only molecular rotation is affected, not the molecular structure. A frequency of 2.45 GHz is preferred in one or more non-limiting exemplary embodiments because it is readily available and has an appropriate penetration depth to interact with a sample. Electromagnetic wave energy includes an electric field and a mutually perpendicular magnetic field, though primarily only the electric field transfers energy to heat a substance. Electromagnetic waves couple instantly and directly with molecules in a specimen (unlike conductive heat where the vessel holding the specimen needs to heat first). Any material that will react to either dipole rotation or ionic conduction will instantly and locally start heating. Advantageously, electromagnetic waves exhibit an “instant on-instant off” property such that when the electromagnetic wave energy is turned off, the heat that resulted from the waves is all that remains, and it dissipates into the environment over time. Electromagnetic waves can be provided to a sample, for example, through a vessel wall that is transparent to electromagnetic wave energy.
As will be appreciated by the skilled artisan, in a positive tone resist, the resist is exposed where the underlying material is to be removed; the exposure changes the resist so that it becomes more soluble in the developer. The exposed resist is then washed away leaving regions of the underlying material. Negative tone resists behave in the opposite manner; when exposed, the negative resist becomes more difficult to dissolve in developer, and therefore remains on the surface after exposure—the developer solution removes only the unexposed areas.
For a first exemplary process flow consider
In
As shown in
The first exemplary process flow can thus be summarized as deposition/growth of a blanket film including a reactive material of interest, over a conductor (metal)-dielectric pattern of interest, as in
We have performed experiments and simulations that are discussed further elsewhere herein.
For a second exemplary process flow, consider
In
The second exemplary process flow can thus be summarized as applying electromagnetic waves to a conductor (metal)-dielectric pattern, thereby creating a well-defined electric field in the dielectric and the region atop the dielectric but not in the metal, as in
Thus,
In at least some aspects, vapor phase processes may be preferred to liquid phase. One or more embodiments are particularly advantageous for small feature sizes. Alignment is a significant issue at small feature sizes. For example, for 200 nm wide copper lines, one could, in principle, carry out a patterning step. However, if 20 nm wide copper lines are desired, alignment will be challenging. Advantageously, in one or more embodiments, the use of electromagnetic waves to induce local chemical reaction results in a self-aligned system. Self-alignment relates to both liquid and vapor phase aspects.
Refer now to
As noted, by definition, no electric field exists in metals (they reflect electromagnetic waves). However, free electrons (e−) in the metal move around and follow the electromagnetic wave electric field. In turn, the electric field lines are modified and strengthened in the dielectric in between the metal lines. The electric field lines are also “pretty strong” on top of the dielectric itself (i.e., relative to the surface atop the metal). When applied on a metal-dielectric pattern, the electric field is primarily concentrated in between the metal lines (i.e. in the dielectric, as well as in the region atop the dielectric). The application of electromagnetic waves to a metal-dielectric pattern will readily create a localized undulating electric field/energy profile inside and outside the dielectric material. A strong enough localized electric field can trigger localized chemical reaction/material transformation on top of the dielectric (while no measurable reaction takes place on top of the metal). In addition, electromagnetic waves whose frequency is resonant with the choice of ALD precursors for Area Selective Deposition (ASD) will advantageously have a larger effect on localized deposition atop the dielectric surface.
One or more embodiments advantageously operate in a regime where minimal heating of the patterned substrate occurs. This can be achieved by either reducing the energy/amplitude/power of the continuously applied electromagnetic wave, and/or by applying a periodic train of short pulses of the electromagnetic wave where the duty cycle doesn't allow appreciable heating of the sample. We have found that applying short electromagnetic wave pulses (with enough delay in between pulses) to the sample is one way to controllably deposit a precursor while preventing the system from excessively heating up.
We have carried out experimental simulations using finite element software (Ansys® HFSS 3D High Frequency Structure Simulation Software (registered mark of ANSYS, INC. CANONSBURG PENNSYLVANIA USA)).
It is worth noting that ALD precursors are quite polar. They will strongly couple to the electric field thereby preferentially congregating in the high electric field regions. When the electromagnetic radiation is applied, the electrons in the metal will also respond, causing the metal to heat. However, one or more embodiments do not rely on conductive heating from the metal onto the precursor/photoresist-rather, one or more embodiments employ very short electromagnetic wave durations to deliberately avoid heating that would degrade the resist, ALD precursor, or the sample specimen. Consider, for example, application of a continuous electromagnetic wave where the amplitude has been sufficiently reduced such that the whole chip has only heated up to 40-50° C. in equilibrium. In such a case, none of the resist will “cook.” Still, however, the electric field will only be high on top of the dielectric. If precursors are introduced (see, e.g., vapor phase precursor introduction in
Example results will now be discussed with regard to applying the first exemplary process flow of
Referring to
In experiments, we have been able to remove more of the photo resist on top of the copper.
To demonstrate reproducibility, experiments were repeated.
In an example, 1000 Watts is applied for about 50-100 ms, waiting about 3 seconds between pulses for cooling. In an example, 1000 Watts is applied for 2 seconds without pulsing. Generally, better results would be anticipated with pulsing or with a lower wattage if there is no pulsing. Required wattage values are, of course, configuration-dependent, and could be determined by the skilled artisan from, for example, finite element analysis considering thermal and electromagnetic effects. Even better results can be anticipated with a more sophisticated electromagnetic wave device.
Thus, it should be noted that the electromagnetic wave amplitude and/or duration that is appropriate will vary based on the specific system including, for example, the number of layers of metallization. In one aspect, the electromagnetic wave amplitude and/or duration are controlled such that the temperature anywhere in the structure does not exceed 400 degrees C., or 275 degrees C., or 150 degrees C. The temperature in the photoresist could also be controlled to a certain value, in addition to and/or in lieu of controlling the overall temperature. Wattage values and other parameters needed to control, the temperature to a certain value are, of course, configuration-dependent, and could be determined by the skilled artisan from, for example, finite element analysis considering thermal and electromagnetic effects.
One or more embodiments are thus substantially different from prior art approaches where the goal of applying electromagnetic waves is to deliberately heat up metal sheets or to trigger chemical reactions through deliberate bulk conductive heating. In contrast, one or more embodiments are localized and selective. In one or more embodiments, while local heating of the dielectric is expected for short electromagnetic wave durations, this is unlike prior art approaches which deliberately rely on bulk conductive heating from the metal lines (e.g. copper). One or more embodiments instead rely on limited heating of the dielectric, without directly heating the metal. Indeed, one or more embodiments provide electromagnetic wave assisted localized deposition due to the localized electric field rather than deliberate bulk conductive heating. In one or more embodiments, the localized electric field on top of the dielectric surface in a metal-dielectric pattern affects localized chemistry without substantially raising the sample temperature (as noted above, in one or more embodiments, at the scale of individual molecules impacted by the electromagnetic field, the kinetic energy may be very high, corresponding theoretically to hundreds or thousands of degrees C. (recall that the temperature of a substance is related to the average kinetic energy of its particles). However, pertinently, on a macroscopic level, the average temperature is only, for example, 40-50° C.).
Given the teachings herein, for any elements for which example materials are not set forth, the skilled artisan can select appropriate materials, and for any fabrication steps for which specific exemplary processes have not been set forth, the skilled artisan can select appropriate known processes. One or more embodiments can be used wherever metal lines are desired, especially narrow (10 nm or less) self-aligned metal lines. Some embodiments can be used for back-end-of-line (BEOL) wiring that connects to a device layer (e.g., field effect transistors such as nanosheet field effect transistors) using vias. Exemplary known processes, in no particular order, include, for example, preparation (deposition/patterning) of nanosheet stacks with sacrificial SiGe regions, etch-back of sacrificial SiGe, formation of shallow trench isolation (STI), dummy gates including gate spacers, inner spacers, and dielectric isolation, dummy gate open, dummy gate removal, channel release, high-K metal gate (HKMG) stack deposition, self-aligned contact (SAC) cap and trench metal contact formation, and with lithography, masks, and patterning, generally. The skilled artisan will be familiar with the “dummy gate” process for forming HKMGs. More generally, the skilled artisan will be familiar with epitaxial growth, self-aligned contact formation, formation of high-K metal gates, and so on. The term “high-K” has a definite meaning to the skilled artisan in the context of high-K metal gate (HKMG) stacks, and is not a mere relative term.
Many different substrates can be used; non-limiting examples include bulk silicon, glass, sapphire, GaAs, and the like.
For any materials and processes not specifically called out, given the teachings herein, the skilled artisan can adapt standard techniques to implement one or more embodiments.
Semiconductor device manufacturing includes various steps of device patterning processes. For example, the manufacturing of a semiconductor chip may start with, for example, a plurality of CAD (computer aided design) generated device patterns, which is then followed by effort to replicate these device patterns in a substrate. The replication process may involve the use of various exposing techniques and a variety of subtractive (etching) and/or additive (deposition) material processing procedures. For example, in a photolithographic process, a layer of photo-resist material may first be applied on top of a substrate, and then be exposed selectively according to a pre-determined device pattern or patterns. Portions of the photo-resist that are exposed to light or other ionizing radiation (e.g., ultraviolet, electron beams, X-rays, etc.) may experience some changes in their solubility to certain solutions. The photo-resist may then be developed in a developer solution, thereby removing the non-irradiated (in a negative resist) or irradiated (in a positive resist) portions of the resist layer, to create a photo-resist pattern or photo-mask. The photo-resist pattern or photo-mask may subsequently be copied or transferred to the substrate underneath the photo-resist pattern.
There are numerous techniques used by those skilled in the art to remove material at various stages of creating a semiconductor structure. As used herein, these processes are referred to generically as “etching”. For example, etching includes techniques of wet etching, dry etching, chemical oxide removal (COR) etching, and reactive ion etching (RIE), which are all known techniques to remove select material(s) when forming a semiconductor structure. The Standard Clean 1 (SC1) contains a strong base, typically ammonium hydroxide, and hydrogen peroxide. The SC2 contains a strong acid such as hydrochloric acid and hydrogen peroxide. The techniques and application of etching is well understood by those skilled in the art and, as such, a more detailed description of such processes is not presented herein.
Although the overall fabrication method and the structures formed thereby are novel, certain individual processing steps required to implement the method may utilize conventional semiconductor fabrication techniques and conventional semiconductor fabrication tooling. These techniques and tooling will already be familiar to one having ordinary skill in the relevant arts given the teachings herein. For example, the skilled artisan will be familiar with epitaxial growth, self-aligned contact formation, formation of high-K metal gates, and so on. The term “high-K” has a definite meaning to the skilled artisan in the context of high-K metal gate (HKMG) stacks, and is not a mere relative term. Moreover, one or more of the processing steps and tooling used to fabricate semiconductor devices are also described in a number of readily available publications, including, for example: James D. Plummer et al., Silicon VLSI Technology: Fundamentals, Practice, and Modeling 1st Edition, Prentice Hall, 2001 and P. H. Holloway et al., Handbook of Compound Semiconductors: Growth, Processing, Characterization, and Devices, Cambridge University Press, 2008, which are both hereby incorporated by reference herein. It is emphasized that while some individual processing steps are set forth herein, those steps are merely illustrative, and one skilled in the art may be familiar with several equally suitable alternatives that would be applicable.
It is to be appreciated that the various layers and/or regions shown in the accompanying figures may not be drawn to scale. Furthermore, one or more semiconductor layers of a type commonly used in such integrated circuit devices may not be explicitly shown in a given figure for ease of explanation. This does not imply that the semiconductor layer(s) not explicitly shown are omitted in the actual integrated circuit device.
Those skilled in the art will appreciate that the exemplary structures discussed above can be distributed in raw form (i.e., a single wafer having multiple unpackaged chips), as bare dies, in packaged form, or incorporated as parts of intermediate products or end products.
An integrated circuit in accordance with aspects of the present inventions can be employed in essentially any application and/or electronic system. Given the teachings of the present disclosure provided herein, one of ordinary skill in the art will be able to contemplate other implementations and applications of embodiments disclosed herein.
The illustrations of embodiments described herein are intended to provide a general understanding of the various embodiments, and they are not intended to serve as a complete description of all the elements and features of apparatus and systems that might make use of the circuits and techniques described herein. Many other embodiments will become apparent to those skilled in the art given the teachings herein; other embodiments are utilized and derived therefrom, such that structural and logical substitutions and changes can be made without departing from the scope of this disclosure. It should also be noted that, in some alternative implementations, some of the steps of the exemplary methods may occur out of the order noted in the figures. For example, two steps shown in succession may, in fact, be executed substantially concurrently, or certain steps may sometimes be executed in the reverse order, depending upon the functionality involved. The drawings are also merely representational and are not drawn to scale. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
Embodiments are referred to herein, individually and/or collectively, by the term “embodiment” merely for convenience and without intending to limit the scope of this application to any single embodiment or inventive concept if more than one is, in fact, shown. Thus, although specific embodiments have been illustrated and described herein, it should be understood that an arrangement achieving the same purpose can be substituted for the specific embodiment(s) shown; that is, this disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will become apparent to those of skill in the art given the teachings herein.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. 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, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. Terms such as “bottom”, “top”, “above”, “over”, “under” and “below” are used to indicate relative positioning of elements or structures to each other as opposed to relative elevation. If a layer of a structure is described herein as “over” another layer, it will be understood that there may or may not be intermediate elements or layers between the two specified layers. If a layer is described as “directly on” another layer, direct contact of the two layers is indicated. As the term is used herein and in the appended claims, “about” means within plus or minus ten percent.
The corresponding structures, materials, acts, and equivalents of any means or step-plus-function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the various embodiments has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the forms disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit thereof. The embodiments were chosen and described in order to best explain principles and practical applications, and to enable others of ordinary skill in the art to understand the various embodiments with various modifications as are suited to the particular use contemplated.
The abstract is provided to comply with 37 C.F.R. § 1.76 (b), which requires an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the appended claims reflect, the claimed subject matter may lie in less than all features of a single embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as separately claimed subject matter.
Given the teachings provided herein, one of ordinary skill in the art will be able to contemplate other implementations and applications of the techniques and disclosed embodiments. Although illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that illustrative embodiments are not limited to those precise embodiments, and that various other changes and modifications are made therein by one skilled in the art without departing from the scope of the appended claims.
