Zinc, zinc-containing film deposition and zinc-containing alloy formation using zinc and hydrogen sources

Abstract

A process is disclosed by which a Zinc containing material is deposited by a vapor phase deposition onto a metallic substrate. The process includes use of a strong reducing agent to produce a deposited material with metallic Zn. The metallic Zinc may penetrate into the metallic substrate to form a Zinc alloy thereof extend from the surface into the substrate material.

Description

[0001]2022P00239 ZINC, ZINC-CONTAINING FILM DEPOSITION AND ZINC-CONTAINING ALLOY FORMATION USING ZINC AND HYDROGEN SOURCES Cross Reference to Related Applications This application claims priority to U.S. provisional patent application No. 63 / 541,790, filed September 30, 2023, the entire contents of which are incorporated herein by reference. Technical Field This disclosure relates to vapor deposited films containing metallic zinc. Background Art The most commonly used zinc precursor genus used in chemical vapor phase deposition (CVD) is the dialkylzinc (DAZ) genus, the most common of which is diethylzinc (DEZ). The state of the art describes various attempts to deposit metallic zinc by a chemical vapor phase deposition process using a DAZ species. The most successful of these, to the inventors’ knowledge, is described in James, W. J., and Pei^Li Tseng. "Synthesis and characterization of zinc thin films formed in a glow discharge." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 3.6 (1985): 2634-2638. Unfortunately, this technique requires plasma polymerization of DEZ and the process exhibits “strange and unique phenomena of Zn deposition” that render the process unlikely to be commercially useful. DEZ has also been used to deposit high purity zinc metal films using laser CVD. Borsella, E., and R. Larciprete. "Excimer laser photolysis of organometallic compounds for Zn deposition." Applied surface science 36.1-4 (1989): 221-230. Laser CVD is not used commercially today and would be difficult to adapt to high volume or high surface area depositions in an economically viable manner. The inventors are unaware of any thermal vapor deposition under 300 degrees C that results in a deposited material having at least 20% (atomic) metallic zinc. The problem to be solved is to develop a thermal CVD or atomic layer deposition (ALD) process using a Q-Zn-alkyl chemical (with Q being a second alkyl or a heteroligand), preferably DAZs, to produce a deposit having at least some 2022P00239 appreciable amount of metallic zinc (≥ 20% Zn0). The substrates of particular interest are metallic substrates having a conductivity of about 10-2A / m or more (e.g. aluminum, iron, cobalt, nickel, copper, platinum, lanthanide, or metal alloys having these metals as alloy components). In addition, due to thermal budget limitations for many substrates and manufacturing processes, the thermal CVD should be conducted at less than 350 degrees C, and ideally at 200 degrees C or less. Summary of Invention The invention may be understood in relation to the following embodiments presented as numbered sentences: 1. A sequential vapor deposition process for forming a zinc-containing material on a substrate, the process comprising the steps of: a) first exposing the substrate to a vapor of a dialkyl zinc chemical, b) then exposing the substrate from step a) to a vapor of a hydrogen containing reducing agent, wherein the reducing agent has a stronger reducing potential than hydrogen gas, c) forming a zinc-containing deposit on a surface of the substrate, wherein the zinc-containing deposit comprises a metallic zinc. 2. The sequential vapor deposition process of sentence 1, further comprising a purge step between steps a) and b), wherein a purge gas volume is applied to the substrate to remove a portion of the dialkyl zinc chemical after step a) and / or a portion of the vapor of the reducing agent after step b). 3. The sequential vapor deposition process of sentence 1 or 2, wherein the sequential vapor deposition process is a thermal chemical vapor deposition process. 4. The sequential vapor deposition process of sentence 1 or 2, wherein the sequential vapor deposition process is a thermal atomic layer deposition process. 5. The sequential vapor deposition process of any one of sentences 1-4, wherein the sequential vapor deposition process excludes a) a photolysis of the dialkyl zinc chemical; and / or b) the formation of a plasma of the reducing agent and / or c) a formation of a plasma of the dialkyl zinc chemical. 6. The sequential vapor deposition process of any one of sentences 1-5, wherein the substrate is a metallic substrate, preferably having a conductivity of about 2022P00239 10-2A / m or more. 7. The sequential vapor deposition process of sentence 6, wherein the metallic substrate comprises aluminum, iron, cobalt, nickel, copper, platinum, an element of the lanthanide series, or metal alloys having one or more of the foregoing, preferably comprising at least 20% of one or more of the foregoing metals by atomic percentage. 8. The sequential vapor deposition process of sentence 6, wherein the metallic substrate comprises at least 10% iron, preferably at least 50% iron, such as at least 75% iron, by atomic percentage. 9. The sequential vapor deposition process of any one of sentences 1-8, wherein the dialkyl zinc chemical comprises one or more of ZnMe2, ZnEt2, Zn(iPr)2, (N,N,N'-Triethylenediamine)ZnMe2, and (N,N,N'-Triethylenediamine)ZnEt2. 10. The sequential vapor deposition process of any one of sentences 1-8, wherein the reducing agent comprises a boron containing chemical, preferably selected from one or more of: a) R3R4BH, wherein each R3, R4is independently selected from hydrogen (H); or a N, C, O, F and / or S-containing non-neutral linear, branched or cyclic moiety (for example an alkyl, an alkene, an aryl, a phenoxide, an amide, an alkoxide, a thiolate); b) L2-BH3, wherein L2is a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand (for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes); c) L3L4B2H4, wherein L3, L4are each independently selected from hydrogen; or a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand (for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes); and d) M(BH4)x, wherein M is a metal and x is the metal valency, such as Zirconium Borohydride (Zr(BH4)4), Hafnium Borohydride (Hf(BH4)4), Aluminum Borohydride (Al(BH4)3), Zinc Borohydride (Zn(BH4)2) and their derivatives. 11. The sequential vapor deposition process of sentence 10, wherein the boron containing chemical comprises one or more R3R4BH chemicals, such as pinacolborane, catecholborane, disiamylborane, Cy2BH, 9-BBN, and thexylborane. 2022P00239 12. The sequential vapor deposition process of sentence 10, wherein the boron containing chemical comprises one or more L2-BH3chemicals, such as (THF)BH3, Me2S-BH3, Et3N-BH3, Me2NH-BH3, Py-BH3, Ph3P-BH3, (Ph2PH)BH3, (tBu2PH)BH3, H3N-BH3, and tBuNH2)BH3. 13. The sequential vapor deposition process of sentence 10, wherein the boron containing chemical comprises one or more L3L4B2H4chemicals, such as B2H6, (PMe3)2B2H4 and (Me2PCH2PMe2)B2H4. 14. The sequential vapor deposition process of any one of sentences 1-13, wherein a substrate temperature during steps a) and b) is from 100 degrees C to 300 degrees C, preferably from 150 degrees C to 250 degrees C, more preferably from 175 degrees C to 225 degrees C, even more preferably from 175 degrees C to 200 degrees C. 15. The sequential vapor deposition process of any one of sentences 1-14, wherein the metallic zinc from the zinc-containing deposit penetrates into the substrate to add a metallic zinc to at least an outer portion of the substrate, said added metallic zinc extending from the surface of the substrate into the substrate. 16. The sequential vapor deposition process of any one of sentences 1-15, wherein a substrate temperature is selected so that the zinc-containing deposit comprises less than 10 atomic percent of an heteroatom derived from the hydrogen containing reducing agent, such as less than 10% or less than 5% boron derived from a boron containing chemical. Disclosure of Invention Embodiments of the present invention provide a novel approach for the deposition and subsequent diffusion of zinc atoms into metallic substrates having a conductivity of about 10-2A / m or more (e.g. aluminum, iron, cobalt, nickel, copper, platinum, lanthanide, or metal alloys having one or more of the foregoing) to form Zn alloys or metal zinc coatings, using sequential or continuous flow thermal CVD, or ALD, without forming a plasma and without laser assisted photodecomposition. The process involves the reaction of a Q-Zn-alkyl chemical, preferably a dialkyl zinc- precursor (DAZ), with a hydrogen-containing reducing agent having a reducing power greater than hydrogen gas (H2) and which preferably does not contaminate the resulting Zn layer with hetero-atoms in a significant manner. Preferably, the deposition process consists of sequential pulses ( ALD or pulsed CVD) of a DAZ and then a 2022P00239 reducing agent. The deposition process is normally performed at temperatures ranging from 100 degrees C to 350 degrees C, preferably 150-300 degrees C, such as 175- 225 degrees C.. The reducing agent is preferably a borane such as pinacolborane, aminoboranes, and / or diborane. Other reductants may be included such as alanes, silanes, germanes, stannanes, amines, and phosphines. In some embodiments, the reducing agent is a borane and the resulting film also contains a Boron concentration ranging from 0.1% to 10%, preferably 0.1 to 3%. The process yields uniform and conformal deposition of zinc metal-containing films. The metallic substrate can be in the form of flat surfaces, such as foils, or a complex form, like patterned substrates, rods, structured rods, or powders. The zinc source is a zinc alkyl compound, or adduct thereof, such as ZnMe2, ZnEt2, Zn(iPr)2, (TEEDA)ZnMe2, or (TEEDA)ZnEt2. ZnEt2(“DEZ”) is preferred. The preferred reductant is a borane with the general formulas (I), (II), and (III) can be included: R3R4BH (I), L2-BH3 (II), and L3L4B2H4 (III). Each R3, R4is independently selected from hydrogen (H) or a N, C, O, F and / or S-containing non-neutral linear, branched or cyclic moiety, for example an alkyl, an alkene, an aryl, a phenoxide, an amide, an alkoxide, a thiolate. L2is a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes. L3, L4are each independently selected from hydrogen or a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand, for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes. Selected representative examples of R3R4BH (I) are pinacolborane, catecholborane, disiamylborane, Cy2BH, 9-BBN, and thexylborane. Selected representative examples of L2-BH3(II) are (THF)BH3, Me2S-BH3, Et3N-BH3, Me2NH-BH3, Py-BH3, Ph3P-BH3, (Ph2PH)BH3, (tBu2PH)BH3, H3N-BH3, and tBuNH2)BH3. Selected representative examples of L3L4B2H4(III) are B2H6, (PMe3)2B2H4and (Me2PCH2PMe2)B2H4. 2022P00239 The reducing agent can also be selected from the group consisting of volatile metal borohydrides having generic formula M(BH4)x, such as, but not limited to, Zirconium Borohydride (Zr(BH4)4), Hafnium Borohydride (Hf(BH4)4), Aluminum Borohydride (Al(BH4)3), Zinc Borohydride (Zn(BH4)2) and their derivatives. Brief Description of Drawings Figure 1 shows the etching profile atomic composition for the exemplary iron foil substrate used in the experiments herein (control); Figure 2A and 2B shows a vapor deposition with DEZ alone (2A) and DEZ plus diborane (2B); and Figure 3 shows the etching profile atomic composition for a DEZ thermal deposition using 4% Hydrogen gas in Nitrogen as the reducing agent. Detailed Description of the Preferred Embodiments Generally the new method is performed by sequential pulse CVD or ALD, by first exposing a metallic substrate to the DAZ chemical, preferably DEZ, and then exposing the substrate to the reducing agent, preferably a borane chemical such as diborane. Preferably there is an intervening purge step with an inert gas such as Nitrogen or Argon. The “cycle” of Daz-purge-Reducing Agent-purge, is normally repeated until the desired amount of zinc-containing material has been deposited on the substrate. In some embodiments, within an “ALD window” the deposition process is self limiting and thus an atomic layer deposition process. The deposition process is normally performed in a temperature range of 150 degrees C to 300 degrees C, with 175-225 degrees C being preferred in many embodiments for a maximum quantity of zinc deposited. While atmospheric pressure processes are possible, generally the process herein is preferably performed in a vacuum chamber having sub atmospheric pressure, such as 0.1 to 10 torr, most preferably about 1 torr. In a primary subset of embodiments, the process results in metallic zinc on the surface and also penetrating the surface of the substrate to form an alloy of the original substrate material and the deposited Zinc. Some Zinc Oxide deposition may also occur, with the ZnO content being concentrated at the surface of the material. An important parameter for controlling the ratio of ZnO / Zn0is the state of surface oxidation of the substrate and the amount of environmental oxygen source(s) in the process gas 2022P00239 (such as from air leaks into a vacuum chamber). Examples Representative Experiment 1 - Iron foil control Untreated iron foil substrate was analyzed for its atomic percent composition as a function of etch time. Figure 1 shows that there is no Zn or Boron (below instrument detection limit). Note that the surface has some oxide and Carbon contamination. The Iron foil was thermally treated to remove some of the Carbon contamination and oxidation prior to use in the following deposition experiments (450 degrees C for 2 hrs under 4%H2 / N2 mixture). The general cyclic deposition parameters and conditions used in the following experiments were: 2022P00239 Diborane was selected as a representative reducing agent. The diborane was supplied in gas pulses of 10%(vol) diborane / balance N2 gas (same N2 as the purge gas used). Representative Experiment 1 - Iron foil DEZ only vs DEZ+B2H6 at 200 degrees C Using the above parameters, without the diborane pulses, resulted in a low amount of Zn deposition on the foil surface, which was essentially entirely ZnO. Figure 1 A shows the Atomic Percent composition of the foil after deposition. At 20 seconds of etching, the composition was: In contrast, adding the diborane pulses to the cycle yielded the Atomic Percent composition shown in Figure 1B. At 20 seconds of etching, the composition was: A very small amount of boron is present, which is not expected in most uses to be a problem. The Zinc content is dramatically increased (53 fold). In addition to the amount of Zinc deposited, the substrate penetration and oxidation states are noteworthy. As shown in Figure 2A, the small amount of Zn, deposited by DEZ exposure alone, was surface deposited and in the form of Zinc Oxide. Figure 2B, showing the addition of diborane, also resulted in a surface layer of ZnO, but quickly shifting to a mix of ZnO / Zn0, with the metallic Zinc penetrating into the iron foil substrate with limited oxidation. This unique and unexpected phenomenon 2022P00239 creates opportunities to add metallic zinc to a variety of substrates in a commercially feasible manner, without damaging plasma or exotic laser techniques that are not viable for commercial production. Experiments at 150 degrees C followed the same pattern as the 200 degree C deposition, but with approximately one third of the amount of Zinc and Boron being deposited. It is projected that the process will be commercially unsuitable below this temperature, although the process should result in some deposition and Zinc penetration even as low as 100 degrees C. It is possible that this very low temperature process may still be useful for certain applications. Representative Experiment 2 - DEZ and DEZ+B2H6 at 250 degrees C Conditions were unchanged from Experiment 1 except that the temperature was increased to 250 degrees C. DEZ alone again produced a surface deposit of ZnO with no measurable Zn metal component and which did not penetrate into the iron foil. In contrast to Experiment 1, the addition of diborane again produced a thermal deposit having some ZnO on the outer surface, but again transitioning into a non-oxide deposit, which again penetrated into the underlying substrate to a similar degree. The main difference at this temperature was the Boron content. The deposited material at 20 seconds etching had 32.5% Boron and the Zn penetrating into the foil appeared to be mostly in the form of ZnB. Thus, at least with diborane, 250 degrees C is too hot to produce the desired Zn metal. However there could be other applications where the ZnB would be desirable. It is expected that mono-Boron based reducing agents will reduce the amount of Boron deposited and allow for metallic Zinc deposition at 250 degrees C, even up to 300 degrees C. Comparison Data - DEZ with 4% (vol) H2gas (balance N2) as a reducing agent. As shown in Figure 3, H2 gas at 200 degrees C has insufficient reducing power to yield metallic Zinc in the process. Only a small amount of ZnO is formed on the surface. At 20 seconds of etching, the atomic composition was: 2022P00239 The Boron comes from residual diborane that had not been fully flushed from the reactor. Even in the presence of this residual diborane, the hydrogen gas was incapable of producing metallic Zn. Reducing power is measured as the redox standard potential in volts ( ), with H2 gas defined as 0.00 volts whereas diborane is {-0.368}. Because the amount of Boron in the deposited materials is negligible at 200 degrees C, the working theory is that diborane’s effect is through reduction of the Zn being deposited to reduce the amount of ZnO formation. This is consistent with the increased metallic zinc proportion of the zinc penetrating into the substrate. Once the metallic zinc migrates from the surface into the substrate, that penetrating zinc is protected from oxidation. On this basis, other reducing agents, which can be provided in the temperature range as a vapor, and therefore are suitable for use in CVD and ALD, may be selected based on their reduction potential to produce similar results as shown for diborane. Industrial Applicability The present invention is at least industrially applicable to the formation of metallic zinc containing materials for such applications as semiconductor manufacturer and optical coatings and any other kind of applications requiring Zinc metal. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step. The singular forms "a", "an" and "the" include plural referents, unless the context clearly dictates otherwise. 2022P00239 "Comprising" in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of “comprising”). “Comprising” as used herein may be replaced by the more limited transitional terms "consisting essentially of" and “consisting of” unless otherwise indicated herein. “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary. Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range. All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited. Technical Definitions As used herein, “room temperature" in the text or in a claim means from approximately 20°C to approximately 25°C. The term “ambient conditions” refers to an environment temperature (i.e., ambient temperature) approximately 20°C to approximately 25°C and an environment pressure (ambient temperature) approximately 1 atm or 1 bar. The term “substrate” refers to a material or materials on which a process is conducted. The substrate may also have one or more layers of differing materials already deposited upon it from a previous manufacturing step. One of ordinary skill in the art will recognize that the terms “film” or “layer” used herein refer to a thickness of some material laid on or spread over a surface and that the surface may be a trench or a line. The standard abbreviations of the elements from the periodic table of elements are used herein. It should be understood that elements may be referred to by these 2022P00239 abbreviations (e.g., Si refers to silicon, N refers to nitrogen, O refers to oxygen, C refers to carbon, H refers to hydrogen, F refers to fluorine, etc.). The unique CAS registry numbers (i.e., “CAS”) assigned by the Chemical Abstract Service are provided to help better identify the molecules disclosed. The Aspect Ratio of a geometric shape is the ratio of its sizes in different dimensions. The aspect ratio is most often expressed as two integer numbers separated by a colon (x:y). The values x and y do not represent actual widths and heights but, rather, the proportion between width and height. As an example, 8:5, 16:10, 1.6:1 are all ways of representing the same aspect ratio. In objects of more than two dimensions, such as hyperrectangles, the aspect ratio can still be defined as the ratio of the longest side to the shortest side. Conformality and Step Coverage both refer to the degree of variability in the thickness of a film on a surface, especially topologically different areas of a surface. This is especially relevant to surfaces with microstructures having various aspect ratios. Complete (100%) conformality for the above example means there is zero cusping and the top surface, the trench sidewall and when applicable the trench bottom, have all identical thicknesses. If a single conformality percentage is given, it is the least conformal measurement corresponding to the greatest deviation in relative thickness of the overall film at two selected points on the surface. The two points may correspond to the highest Aspect Ratio points or, for example, points having a specific Aspect Ratio such as 6:1 or less. Thicknesses of films are assessed by a number of methods, for example scanning electron microscopy of sectioned substrates. A film is generally “conformal” if the film is at least 20% conformality, preferably at least 50%.

Claims

2022P00239 CLAIMS:

1. A sequential vapor deposition process for forming a zinc-containing material on a substrate, the process comprising the steps of: a) first exposing the substrate to a vapor of a dialkyl zinc chemical, b) then exposing the substrate from step a) to a vapor of a hydrogen containing reducing agent, wherein the reducing agent has a stronger reducing potential than hydrogen gas, c) forming a zinc-containing deposit on a surface of the substrate, wherein the zinc-containing deposit comprises a metallic zinc.

2. The sequential vapor deposition process of claim 1, further comprising a purge step between steps a) and b), wherein a purge gas volume is applied to the substrate to remove a portion of the dialkyl zinc chemical after step a) and / or a portion of the vapor of the reducing agent after step b).

3. The sequential vapor deposition process of claim 1 or 2, wherein the sequential vapor deposition process is a thermal chemical vapor deposition process.

4. The sequential vapor deposition process of claim 1 or 2, wherein the sequential vapor deposition process is a thermal atomic layer deposition process.

5. The sequential vapor deposition process of any one of claims 1–4, wherein the sequential vapor deposition process excludes a) a photolysis of the dialkyl zinc chemical; and / or b) the formation of a plasma of the reducing agent and / or c) a formation of a plasma of the dialkyl zinc chemical.

6. The sequential vapor deposition process of any one of claims 1–5, wherein the substrate is a metallic substrate, preferably having a conductivity of about 10-2A / m or more.

7. The sequential vapor deposition process of claim 6, wherein the metallic substrate comprises aluminum, iron, cobalt, nickel, copper, platinum, an element of the lanthanide series, or metal alloys having one or more of the foregoing, preferably2022P00239 comprising at least 20% of one or more of the foregoing metals by atomic percentage.

8. The sequential vapor deposition process of claim 6, wherein the metallic substrate comprises at least 10% iron, preferably at least 50% iron, such as at least 75% iron, by atomic percentage.

9. The sequential vapor deposition process of any one of claims 1–8, wherein the dialkyl zinc chemical comprises one or more of ZnMe2, ZnEt2, Zn(iPr)2, (N,N,N'- Triethylenediamine)ZnMe2, and (N,N,N'-Triethylenediamine)ZnEt2.

10. The sequential vapor deposition process of any one of claims 1–8, wherein the reducing agent comprises a boron containing chemical, preferably selected from one or more of: a) R3R4BH, wherein each R3, R4is independently selected from hydrogen (H); or a N, C, O, F and / or S-containing non-neutral linear, branched or cyclic moiety (for example an alkyl, an alkene, an aryl, a phenoxide, an amide, an alkoxide, a thiolate); b) L2-BH3, wherein L2is a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand (for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes); c) L3L4B2H4, wherein L3, L4are each independently selected from hydrogen; or a N, C, O, F and / or S-containing neutral linear, branched or cyclic monodentate or chelate ligand (for example amines, ethers, alkylsulfides, pyridines, phosphines, NHC-carbenes); and d) M(BH4)x, wherein M is a metal and x is the metal valency, such as Zirconium Borohydride (Zr(BH4)4), Hafnium Borohydride (Hf(BH4)4), Aluminum Borohydride (Al(BH4)3), Zinc Borohydride (Zn(BH4)2) and their derivatives.

11. The sequential vapor deposition process of claim 10, wherein the boron containing chemical comprises one or more R3R4BH chemicals, such as pinacolborane, catecholborane, disiamylborane, Cy2BH, 9-BBN, and thexylborane.

12. The sequential vapor deposition process of claim 10, wherein the boron2022P00239 containing chemical comprises one or more L2-BH3 chemicals, such as (THF)BH3, Me2S-BH3, Et3N-BH3, Me2NH-BH3, Py-BH3, Ph3P-BH3, (Ph2PH)BH3, (tBu2PH)BH3, H3N-BH3, and tBuNH2)BH3.

13. The sequential vapor deposition process of claim 10, wherein the boron containing chemical comprises one or more L3L4B2H4chemicals, such as B2H6, (PMe3)2B2H4 and (Me2PCH2PMe2)B2H4.

14. The sequential vapor deposition process of any one of claims 1–13, wherein a substrate temperature during steps a) and b) is from 100 degrees C to 300 degrees C, preferably from 150 degrees C to 250 degrees C, more preferably from 175 degrees C to 225 degrees C, even more preferably from 175 degrees C to 200 degrees C.

15. The sequential vapor deposition process of any one of claims 1–14, wherein the metallic zinc from the zinc-containing deposit penetrates into the substrate to add a metallic zinc to at least an outer portion of the substrate, said added metallic zinc extending from the surface of the substrate into the substrate.

16. The sequential vapor deposition process of any one of claims 1–15, wherein a substrate temperature is selected so that the zinc-containing deposit comprises less than 10 atomic percent of an heteroatom derived from the hydrogen containing reducing agent, such as less than 10% or less than 5% boron derived from a boron containing chemical.

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