Multimodal microstructure material and methods of forming same
11286551 · 2022-03-29
Assignee
Inventors
Cpc classification
C23C14/024
CHEMISTRY; METALLURGY
B82Y40/00
PERFORMING OPERATIONS; TRANSPORTING
C23C28/044
CHEMISTRY; METALLURGY
C23C14/046
CHEMISTRY; METALLURGY
C23C28/30
CHEMISTRY; METALLURGY
C23C28/042
CHEMISTRY; METALLURGY
B82Y30/00
PERFORMING OPERATIONS; TRANSPORTING
International classification
C23C30/00
CHEMISTRY; METALLURGY
Abstract
In a method of forming a metallic material with a multimodal microstructure, nickel is deposited on a substrate having a patterned surface comprising two materials having differing microstructure. The resulting materials may desirably be utilized in semiconductor devices or microelectromechanical (MEMS) devices.
Claims
1. A method of forming a metallic material with multimodal microstructure, the method comprising the steps of: providing a substrate having a patterned surface comprising a first material and a second material, wherein the first material comprises silicon and the second material comprises silicon nitride; and depositing a metallic material directly over the first material and the second material to form a multimodal metallic material, wherein the metallic material comprises nickel, wherein a microstructure of the first material and a microstructure of the second material are different, and wherein a microstructure of the metallic material deposited directly over the first material and a microstructure of the metallic material deposited directly over the second material are different.
2. The method of claim 1, wherein the first material is crystalline.
3. The method of claim 2, wherein the microstructure of the metallic material deposited directly over the first material is crystalline.
4. The method of claim 2, wherein the metallic material deposited directly over the first material is epitaxially grown.
5. The method of claim 1, wherein the second material is not monocrystalline.
6. The method of claim 5, wherein the microstructure of the metallic material deposited directly over the second material is one or more of nanocrystalline structures and ultra-fine grained structures.
7. The method of claim 6, wherein an average cross-sectional dimension of the nanocrystalline structures ranges from about 5 nm to about 100 nm and an average cross-sectional dimension of the ultra-fine grain structures ranges from about 100 nm to about 1000 nm.
8. The method of claim 1, wherein the metallic material comprises elemental metal.
9. The method of claim 1, wherein the metallic material comprises a dilute alloy of nickel.
10. The method of claim 1, wherein a ratio of a surface area of the first material to a surface area of the second material ranges from about 1:0.02 to about 1:50, about 1:0.75 to about 1:1.25, or about 1:0.8 to about 1:1.2.
11. The method of claim 1, wherein the patterned surface comprises a plurality of islands of the first material, the plurality of islands having an average cross-sectional dimensions of about 500 nm to about 50000 nm.
12. The method of claim 1, wherein the patterned surface comprises a plurality of islands of the second material, the plurality of islands having an average cross-sectional dimensions of about 500 nm to about 50000 nm.
13. The method of claim 1, wherein the patterned surface comprises co-continuous or bi continuous or random patterns of the first material and the second material, with cross-sectional dimensions of about 500 nm to about 50000 nm.
14. The method of claim 1, wherein the step of depositing comprises physical vapor deposition.
15. The method of claim 1, wherein a surface of the first material and a surface of the second material are coplanar.
Description
BRIEF DESCRIPTION OF THE DRAWING FIGURES
(1) A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures.
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(13) It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve the understanding of illustrated embodiments of the present disclosure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE DISCLOSURE
(14) The description of exemplary embodiments provided below is merely exemplary and is intended for purposes of illustration only; the following description is not intended to limit the scope of the disclosure or the claims. Moreover, recitation of multiple embodiments having stated features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the stated features.
(15) The present disclosure generally relates to techniques to synthesize metallic or metallic alloy materials (collectively referred to herein as metallic material) or films with precisely controlled multimodal architectures (e.g., grain size distributions and/or grain orientations). The synthesized films include two or more distinct sets of grains that can vary in, for example, mean size, volume fraction and/or spatial distribution/arrangement of the different sets of grains which, in turn, allow tuning of various film/material properties, such as ductility, mechanical energy dissipation, electrical resistivity, thermal conductivity, and the like. Films and materials as described herein can be used in the manufacture of, for example, microelectromechanical systems (MEMS), mechanical damping of micro/nanoscale systems, as coatings for structural materials, and the like.
(16) As used herein, the term “film” refers to material that is deposited onto a surface of a substrate. A film can be continuous or discontinuous.
(17) As used herein, a “substrate” refers to any material having a surface onto which material can be deposited. A substrate can include a bulk material, such as silicon (e.g., single crystal silicon), and may include one or more layers overlying the bulk material. Exemplary materials suitable for use as a substrate include silicon, germanium, silicon germanium, quartz, zinc oxide, and rock salt (NaCl). By way of particular example, a substrate can be or include (111) or (100)-oriented single crystal silicon substrates—e.g., wafers.
(18) Turning now to the figures,
(19) Exemplary first materials can be or include any of the substrate materials noted above. Additionally, or alternatively, a first material can include a buffer material. Exemplary buffer materials include one or more metals, such as one or more metals selected from the group consisting of nickel, copper, vanadium, titanium, aluminum, copper, iron, and silver. Generally, a buffer material grows epitaxially over a monocrystalline material and upon which another monocrystalline material can grow.
(20) Exemplary second materials can be or include, for example, a non-monocrystalline material, such as amorphous or polycrystalline material. Specific examples of second material include materials selected from the group consisting of silicon nitride, silicon oxynitride, aluminum, titanium nitride, and aluminum oxide.
(21) The metallic material can be or include elemental metal or an alloy. Exemplary elemental metals include metal selected from the group consisting of aluminum, copper, iron, nickel, silver, chromium, vanadium, titanium, and cobalt. Exemplary alloys include one or more of dilute alloys of aluminum, copper, iron, silver, nickel, titanium, and chromium, where a dilute alloy includes one of these base metals and up to 10 atomic percent of another metal, such as nickel, iron, copper, cobalt, tantalum, tungsten or manganese.
(22) The figures described below illustrate specific examples of the disclosure. Unless otherwise stated, the invention is not limited to such examples.
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(24) Step 102 can include providing a substrate 202—e.g., a single crystal substrate. The substrate can be or include the first material. Substrate 202 can include any of the first material and/or substrate materials described herein. In the illustrated example, substrate 202 includes bulk material 204, such as bulk semiconductor material (e.g., silicon), and a native oxide layer (e.g., silicon oxide) 206. Oxide layer 206 can be removed using, for example, hydrofluoric acid (e.g., concentration of about 1% to about 49%) at a temperature of about 20° C. to about 50° C.
(25) Next, during step 104, a thin film (e.g., 10-20 nm) of second material—e.g., amorphous (e.g., SiN.sub.x, Al.sub.2O.sub.3, TiN) or polycrystal (e.g., Al, Ag, Cr) layer 208 can be deposited onto a surface of bulk material 204. As illustrated, bulk material 204 may be cleaned or etched prior to the deposition to remove native oxide 206. Layer 208 can be deposited using, for example, low-pressure chemical vapor deposition (CVD), CVD, atomic layer deposition (ALD), physical vapor deposition (PVD) or the like.
(26) Second material layer 208 is then patterned (step 106) with a layer of photoresist 210 and etched (step 108) to expose the underlying single crystal substrate/bulk material 204 (first material) in region 212 and form a patterned amorphous or polycrystal material (second material) in region 214. Patterning can be performed using any suitable (e.g., positive or negative) photoresist and developer to create openings in the photoresist layer 210.
(27) In accordance with examples of the disclosure, second material layer 208 can be dry etched (e.g., using reactive ion etching) or wet etched (e.g., using an appropriate acid or base) or sputter etched (e.g., using Ar or other inert gas ions). The dry etchants can be or include one or more of BCl.sub.3, Cl.sub.2, CF.sub.4, CHF.sub.3, SF.sub.6, O.sub.2 and XeF.sub.2 and their like. The wet etchants can be or include one or more of hydrochloric acid, nitric acid, acetic acid, potassium hydroxide, phosphoric acid, sulfuric acid and the like. A temperature of the etchant can range from about 20° C. to about 80° C. After etching of second material layer 208, hydrofluoric acid (e.g., concentration of about 1% to about 49%) may be used to remove any native oxide layer that has regrown in region 212 and passivate the surface. A surface of first material 204 may remain passivated in region 212 for a period of about 30 to about 60 minutes. Therefore, step 110 may desirably be performed within this window of time.
(28) During step 110, a layer of metallic material 218 can be directly deposited over first/bulk material 204 and second/amorphous/polycrystalline material 208 to form a multimodal metallic material 220. Metallic material 218 can be deposited by, for example, sputtering or other chemical or physical vapor deposition (e.g., evaporation, ablation, or the like) process.
(29) In accordance with examples of the disclosure, a pressure within a reaction chamber during step 110 can range from about 1 mTorr to about 30 mTorr. A temperature within the reaction chamber can range from about 20° C. to about 800° C.
(30) In accordance with various examples of the disclosure, metallic material 218 grows epitaxially as a single crystal material 226 on the first material—e.g., areas 212 where the single crystal substrate is exposed (single-crystal metallic material). In regions 222, where the second material is amorphous or polycrystal layer is present, metallic material 218 grows as a non-monocrystalline or polycrystalline material 224.
(31) When metallic films are grown on amorphous or polycrystalline materials (e.g., second material 208) via physical vapor deposition (PVD) processes, their microstructural evolution is usually governed by the Volmer-Weber mechanism. Volmer-Weber growth is comprised of various stages including nucleation, island formation, coalescence and grain coarsening and typically results in a polycrystalline film. The polycrystalline films often have a specific texture in the growth direction (e.g., (111) texture for face centered cubic metals such as Au and Cu), but the in-plane orientation of the grains is typically random. The grain size in the amorphous/polycrystalline areas can be varied from, for example, tens to hundreds of nanometers to micrometers by altering the film thickness, deposition rate, deposition pressure and/or deposition temperature. For example, the microstructure of the metallic material deposited directly over the second material can include one or more of nanocrystalline and ultra-fine grained—e.g., wherein an average cross-sectional and/or lateral dimension of the nanocrystalline structures ranges from about 5 nm to about 100 nm and an average cross-sectional and/or lateral dimension of the ultra-fine grain structures ranges from about 100 nm to about 1000 nm.
(32) In contrast, metal films deposited on crystalline substrates (e.g., first/bulk material 204) can be made to grow with a specific orientation relationship to the underlying substrate—e.g., the films can be grown epitaxially. This mode of growth can be used to generate single crystal films when the substrate (or other underlying layer) is also monocrystalline.
(33) By designing the mask pattern for the first and/or second material suitably, metal films with specific microstructural architectures and precisely controlled size, spatial distribution/arrangement and volume fraction of nanocrystalline and coarse grains can be synthesized. A ratio of a surface area of the first material to a surface area of the second material can range from, for example, about 1:0.02 to about 1:50, about 1:0.75 to about 1:1.25, or about 1:0.8 to about 1:1.2. The pattern of the first or second material can include a plurality of islands of the first material or the second material, the plurality of islands having an average diameter or cross-sectional/lateral dimension of about 500 nm to about 50000 nm. The pattern of the first material and the second material can also be such that the first and second material are co-continuous, bi-continuous or their like with cross-sectional/lateral dimension of about 500 nm to about 50000 nm.
(34) In accordance with some examples of the disclosure, a surface of the first material and a surface of the second material can be coplanar. An example method of forming coplanar first and second material surfaces is illustrated in
(35) Method 300 includes the steps of providing a substrate (step 302), patterning the substrate (step 304), depositing a second material (step 306), removing patterned features (step 308), and depositing metallic material (step 310).
(36) Step 302 can be the same or similar to step 102. As illustrated in
(37) During step 304, substrate 402 can be patterned and etched. For example, a layer of photoresist can be coated onto a surface of native oxide 406, patterned, and developed to form patterned photoresist features 408. Native oxide layer 406 and bulk/first material 404 can then be etched (e.g., using techniques described above) to form structure 410, which includes etched regions 412.
(38) During step 306, second material 414 is deposited overlying etched regions 412 and photoresist features 408. A thickness of second material 414 can be about the same height as etch regions 412.
(39) Patterned features 408 are removed during step 308. By way of example, the patterned features can be removed using a lift-off process by dissolving the photoresist in a solvent or photoresist stripper, such as acetone or dimethyl sulfoxide at a temperature of about 20° C. to about 150° C. After the removal of photoresist features 408, a planar structure 416 is formed, which includes a first region 418, including first material 404, and a second region 420, including second material 414.
(40) During step 310, a layer of metallic material 428 can be deposited—e.g., as described above—to form structure 422. Structure 422 includes metallic material 428 grown epitaxially as a single crystal material 432 on the first material—e.g., in areas 426 where the single crystal substrate is exposed (single-crystal metallic material). In regions 424 where second material 414 (e.g., amorphous or polycrystal layer) is present, metallic material 428 grows as a polycrystal 430.
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(42) Method 500 includes the steps of providing a substrate (step 502), depositing first/buffer material (step 504), patterning/etching the first/buffer material (step 506), and depositing metallic material (step 508).
(43) Providing a substrate step 502 can be the same or similar as step 102 and/or step 302. As illustrated in
(44) During step 504, a first material 608 is deposited. Prior to depositing first material 608, oxide layer 606 can be removed from a surface of substrate 602. Oxide layer 606 can be removed using, for example, hydrofluoric acid, as described above. Once oxide layer 606 is removed, first material 608 is deposited onto a surface of bulk material or layer 604.
(45) In accordance with exemplary embodiments of the disclosure, first material 608 is or includes a buffer material that is epitaxially grown over bulk material 604. For example, first material 608 can include one or more metals, such as one or more metals selected from the group consisting of Ni, Cu, V, Ti, Al, Cu, Fe, and Ag. First material 608 can be deposited using a variety of techniques, such as PVD (e.g., sputtering or evaporation), CVD, or the like. By way of particular example, the first material can include silver and can be deposited using sputtering. A pressure within a reaction chamber during step 504 can range from about 1 mTorr to about 30 mTorr. A temperature within the reaction chamber during step 504 can range from about 20° C. to about 400° C.
(46) Once first material 608 is deposited, first material 608 can be patterned and etched during step 506. By way of example, a layer of photoresist 610 can be deposited onto first material 608—e.g., using spin-coating techniques. Photoresist 610 can then be patterned and developed to form openings in photoresist 610. Using the patterned photoresist as a mask, first material 608 can be etched to form opening 614. Second material 612, such as an oxide—e.g., a native oxide, can form or be formed in a region defined by opening 614—e.g., upon exposure to an ambient atmosphere. Photoresist 610 can then be removed to form structure 611.
(47) During step 508, metallic material 616 is deposited overlying first material 608 and second material 612. Metallic material 616 can form as a monocrystalline material 618 overlying first material 608 and as a non-monocrystalline material 620 overlying second material 612.
(48) Although the examples above illustrate patterns with substantially uniform sizing for the first material and/or second material, the sizing of the patterns (e.g., for the first and/or second material) can be varied to obtain additional distinct groups of grains.
(49) A size and geometry of coarse grains (obtained via epitaxial growth) can be defined by the patterning (e.g., lithography) process. A size of the finer grains can be altered by changing the deposition temperature, pressure and/or rate. For instance, a mean grain size can be increased by increasing the sputtering rate while keeping all other factors constant. The fine grains can be coarsened, if desired, by post-deposition annealing. Annealing can be performed in an inert gas atmosphere at a temperature of about 100° C. to about 800° C.
(50) In accordance with further examples of the disclosure, an aspect ratio of grains can be controlled. Columnar growth can be suppressed by periodically interrupting the deposition process to produce grains that are more equiaxed. Depending on whether columnar or equiaxed microstructures are desired, continuous or interrupted deposition can be used.
(51) Volume fraction and spatial distribution of grains can also be controlled. A volume fraction of the fine grains can be varied by simply changing the area fraction of the first material on the substrate. Similarly, the spatial distribution of coarse and fine grains and their connectivity can be precisely defined by designing the pattering masks appropriately. Thus, the overall architecture—fine grains embedded in a coarse matrix or isolated coarse grains in a fine matrix or a combination of both—can be tailored as desired.
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(67) Methods of forming a (e.g., multimodal) metallic material can be used to form material or films with desired properties. Such materials or films can be used to form devices, such as semiconductor devices and microelectromechanical devices. For example, the metallic material can be used to form resistive layers with desired/tuned resistivity and cantilevers in microelectromechanical devices.
(68) Although exemplary embodiments of the present disclosure are set forth herein, it should be appreciated that the disclosure is not so limited. For example, although the metallic films are described in connection with various specific materials, the disclosure is not necessarily limited to these examples. Various modifications, variations, and enhancements of the system and method set forth herein may be made without departing from the spirit and scope of the present disclosure.
(69) The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems, components, and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof.