SEED LAYER LASER-INDUCED DEPOSITION

Abstract

A method of creating a layer of a target deposit-material, in a first target pattern, on a substrate surface. The substrate surface is placed in a vacuum and exposed to a first chemical vapor, having precursor molecules for a seed deposit-material, thereby forming a first substrate surface area that has adsorbed the precursor molecules. Then, a charged particle beam is applied to the first substrate surface area in a second target pattern, largely identical to the first target pattern thereby forming a seed layer in a third target pattern. The seed layer is exposed to a second chemical vapor, having target deposit-material precursor molecules, which are adsorbed onto the seed layer. Finally, a laser beam is applied to the seed layer and neighboring area, thereby forming a target deposit-material layer over and about the seed layer, where exposed to the laser beam.

Claims

1. A method comprising; forming a layer of adsorbed seed precursor molecules on a surface of a substrate; irradiating the layer of adsorbed seed precursor molecules with charged particles to form a seed layer; forming a layer of adsorbed target material precursor molecules on the seed layer; and irradiating the layer of adsorbed target material precursor molecules with a pulsed laser beam to form a target deposit layer, wherein no heating of the substrate occurs while irradiating the layer of adsorbed target material precursor molecules with the pulsed laser beam.

2. The method of claim 1, wherein the pulsed laser beam provides ultrashort pulses.

3. The method of claim 1, wherein the seed layer and the target deposit layer are formed from the same material.

4. The method of claim 1, wherein the charged particles are electrons.

5. The method of claim 1, wherein the charged particles are ions.

6. The method of claim 1, further comprising: exposing the surface of the substrate to a first precursor gas, the first precursor gas including the seed precursor molecules; and exposing the surface of the substrate to a second precursor gas, the second precursor gas including the target material precursor molecules.

7. The method of claim 6, wherein the first and second precursor gases are the same.

8. The method of claim 1, wherein the target deposit layer has greater purity than the seed layer.

9. The method of claim 1, further comprising forming a filled closed geometrical shape of at least the target deposit layer.

10. The method of claim 1, wherein the target deposit layer forms at a rate of 0.8 m3/min to 1.5 m3/min.

11. The method of claim 1, wherein forming a layer of adsorbed target material precursor molecules on the seed layer and irradiating the layer of adsorbed target material precursor molecules with a pulsed laser beam are contemporaneously performed.

12. The method of claim 1, wherein the target deposit layer is larger than the seed layer.

13. The method of claim 1, further comprising: forming a second layer of adsorbed seed precursor molecules on the target deposit layer; irradiating the second layer of seed precursor molecules with charged particles to form a second seed layer; forming a second layer of adsorbed target material precursor molecules on the second seed layer; and irradiating the second layer of adsorbed target material precursor molecules with the pulsed laser beam to form a second target deposit layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a more thorough understanding of the present invention, and advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0012] FIG. 1 shows a schematic illustration of a first stage in the process of the present invention;

[0013] FIG. 2 shows a schematic illustration of a final stage of the process of the present invention;

[0014] FIG. 3 shows a plan view of a substrate region after performance of the process stage illustrated in FIG. 1;

[0015] FIG. 4 shows a plan view of the substrate region of FIG. 3 after performance of the process stage illustrated in FIG. 2; and

[0016] FIG. 5 is a flow chart of the process of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0017] Embodiments of the present invention are directed to method of depositing material on a substrate surface.

[0018] Definition: An ultrashort pulsed laser is a laser that emits pulses of light with durations less than 10 picoseconds. Functionally, the ultrashort regime is entered when the intensity dependence of the material response is dominated by the square (or higher order) of the electric field. An ultrashort pulsed laser beam is a beam emitted by an ultrashort pulsed laser.

[0019] Referring to FIGS. 1 and 5, a configuration 110, for implementing a preferred method 210 (FIG. 5) of practicing the present process invention, includes, in a vacuum, a substrate 112 that is exposed to a vapor 114 by a gas injection source 116 (step 212). Typically (but not necessarily), source 116 is a needle positioned less than 1 mm over the surface of substrate 112. Vapor 114 includes precursor molecules for a seed deposit-material, which become adsorbed onto the surface of substrate 112, forming a layer of adsorbed molecules 115 (FIG. 3).

[0020] Irradiation of adsorbed precursor molecules 115 with a charged particle beam 118 (step 214) results in the dissociation of the precursor molecules 115, and a deposit of a seed layer 120, of seed deposit-material. In one preferred embodiment seed layer 120 is a catalytic metal, such as platinum. In this instance, the platinum layer 120 is impure, apparently because the power density of a charged particle beam is insufficient to affect the complete dissociation of the precursor molecules, so carbon and/or other atoms are deposited along with the platinum. A catalytic metal seed layer encourages deposition of target deposit-material by lowering the activation barrier for dissociation of the target deposit-material precursor molecules. In another preferred embodiment, the seed deposit-material changes the sticking coefficient/residence time of the target-deposit material or changes the optical absorption characteristics of the substrate.

[0021] Following the creation of seed layer 120, the charged particle beam 118 is discontinued and the seed layer 120 is exposed to a second vapor 122 (step 216), which has precursor molecules of a target material, which are also adsorbed onto the substrate surface, to form an adsorbed second precursor molecule area 124 (FIG. 4). The area 124 is contemporaneously treated with an ultrashort pulsed laser 126 (step 218). The result is a highly pure deposit 128 of target deposit-material, closely matching, but slightly expanded from, the catalytic seed layer 120. In the case where deposit 128 is of platinum, it is of a much higher purity than the catalytic seed layer 120.

[0022] Although in one preferred embodiment the target material is platinum, there are many other preferred embodiments, each depositing a different material on and about the seed layer. In an alternative preferred embodiment, the target deposit-material is carbon, and carbon precursor molecules are used to provide a carbon deposit 128, on seed layer 120.

[0023] In one preferred embodiment, the charged particle beam spot size on the target is on less than 10 nm. The catalytic see layer 120 is typically wider that the spot size due to the spread of secondary and primary charged particles. The line width of the catalytic seed layer 120 is preferably between 100 and 150 nm, more preferably between 50 and 100 nm, and most preferably between 10 and 50 nm. The line width of the laser-induced deposit is preferably between 110 and 160 nm more preferably between 60 and 110 nm, and most preferably between 15 and 60 nm. The line width which compares favorably to the resultant widths from currently available techniques and may be advantageously used in the creation of micro-circuitry.

[0024] In another preferred method, a wider catalytic seed layer is created, which may have a closed geometric shape, such as a rectangle, either through the use of a wider charged particle beam 118, or through scanning an area with the beam 118. Although other techniques are known for creating a pure layer of material, when there is no restriction as to width, the advantage of the present method is that a layer 120 of pure target material can be created without subjecting the substrate, or the layer 120 as it is being formed, to potentially destructive heat. The techniques described above may be performed at a wide range of temperature, including about 20 C. (approximately room temperature).

[0025] As noted, in a preferred embodiment laser beam 124 is an ultrashort pulsed laser beam. This beam has the advantage of having a fluence that is low enough so that no appreciable ablation or heating of the substrate occurs. In some situations, however, heating the substrate is permissible. Accordingly, in alternative preferred embodiments, another type of laser is used, including picosecond, nanosecond, or continuous wave lasers.

[0026] In one preferred embodiment, vapor 114 includes molecules of trimethyl(methylcyclopentadienyl) platinum, a platinum precursor. In another preferred embodiment, vapor 114 includes molecules of dicobalt octacarbonyl, a cobalt precursor. A skilled person can readily determine other suitable precursor gases for the catalytic layer and for the desired metal layer. Suitable precursors gases for the catalyst layer 120 and the target material deposit layer 128 have the following properties: a high vapor pressure, deposit material-to-ligand bond energy low enough to be disassociated by the charged particle beams but not so low as to spontaneously disassociate, a high sticking coefficient and a long residence time. In one preferred embodiment substrate 112 is a semiconductor substrate, such as a silicon substrate, in another preferred embodiment the substrate is an oxide, such as SiO.sub.2. In general, a wide range of substrates may be used.

[0027] Deposition rates for the seed layer depend on the beam current, but a typical deposition rate is 0.4 um.sup.3/min. Laser-induced deposition of the target material (which may be pure metal) typically occurs at a rate of between 0.8 and 1.2 um.sup.3/min, and more preferably between 1.0 and 1.5 um.sup.3/min. The purity of the laser-induced deposition is typically greater than 40%, more preferably greater than 60%, and most preferably greater than 80%.

[0028] Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0029] In an additional preferred embodiment, the initial seed layer is deposited, and the laser induced deposition process is performed as described above. After this, however, an additional seed layer is deposited, followed again by the laser deposition of a further target-deposit material. This two-layer deposition process is performed iteratively until a desired thickness is reached. This process can be used to cyclically create a layered deposit that adheres more closely to a desired shape and interior structure than would otherwise be possible. In one preferred embodiment, the precursor molecules for the further target deposit-material layers are varied from one deposition cycle to the next, to create an interleaved stack of materials. In this embodiment, the precursor molecules for the charged particle beam-deposited seed layers may also be varied, to optimize for multiple target deposit-material layers. As an example, several differing precursors could be used to create a stack of light emitting materials and metals in-situ to allow for fabrication of a light emitting diode, a diode laser, a quantum well structure, or other light emitting device.

[0030] The following table lists precursor molecules that may be used in the processes described above. This is not a comprehensive list and is provided by way of example.

TABLE-US-00001 TABLE LIST OF PRECURSOR MOLECULES Al(CH.sub.3).sub.3 Trimethyl aluminum AlCl.sub.3 Aluminum trichloride AgBF.sub.4 Silver tetrafluoroborate AuCl.sub.3 Gold trichloride AuCl(PF).sub.3 Gold chloride trifluorophosphine Au(CH.sub.3).sub.2 (acac) Dimethyl gold acac Au(CH.sub.3).sub.2 (hfac) Dimethyl gold hfac Au(CH.sub.3).sub.2(tfac) Dimethyl gold tfac (C.sub.4H.sub.9).sub.4Au.sub.2F.sub.2 Tetrakis isobutyl diaurum difluoride (C.sub.4H.sub.9).sub.2AuF.sub.2Pd(C.sub.6H.sub.11) Bis isobutyl aurum (III) cyclohexyl palladium(II) difluoride Co.sub.2(CO).sub.8 Dicobalt octacarbonyl Co.sub.4(CO).sub.12 Tetracobalt dodecacarbonyl Co(CO).sub.3NO Cobalt tricarbonyl nitrosyl Cr(C.sub.6H.sub.6).sub.2 Diarene chromium Cr(CO).sub.6 Chromium hexacarbonyl Cu-DMB-hfac Copper DMB hfac Cu(hfac).sub.2 Copper di-(hfac) Cu-MHY-hfac Copper MHY hfac Abbreviations: acetylacetonate (acac), hexafluoroacetylacetonate (hfac), trifluoroacetylacetonate (tfac), dimethyl bipyridene (DMB), 2-methyl-1-hexene-3-yne (MHY), vinyltrimethylsilane (VTMS), Cp (cyclopentadienyl)