Nano-scale coatings and related methods suitable for in-vivo use

Abstract

A nano-scale device and method of manufacturing and use. The nano-scale device may be used in-vivo and may comprise a fluid path with an inlet microchannel, an outlet microchannel, and a nanochannel. The fluid path comprises a bio-robust material. In certain embodiments, the bio-robust material may be coated over a material that is not bio-robust.

Claims

1. A nanochannel delivery device comprising: an inlet microchannel comprising a first sidewall; an outlet microchannel comprising a second sidewall; and a nanochannel etched between a first bio-robust layer and a second bio-robust layer, wherein: the first bio-robust layer is a silicon carbide layer; the second bio-robust layer is a silicon carbide layer; the etched nanochannel is in fluid communication with the inlet microchannel and the outlet microchannel; the inlet microchannel comprises a first bio-robust coating on the first sidewall of the inlet microchannel, wherein the first bio-robust coating is a tantalum oxide coating; the outlet microchannel comprises a second bio-robust coating on the second sidewall of the outlet microchannel, wherein the second bio-robust coating is a silicon carbide coating; and the first bio-robust coating is atomically sealed to the first bio-robust layer; and the second bio-robust coating is atomically sealed to the second bio-robust layer.

2. The nanochannel delivery device of claim 1 wherein the inlet microchannel comprises the first bio-robust coating atomically sealed to a non-bio-robust material.

3. The nanochannel delivery device of claim 1 wherein the outlet microchannel comprises the second bio-robust coating atomically sealed to a non-bio-robust material.

4. The nanochannel delivery device of claim 1 wherein: the first bio-robust coating is atomically sealed to the second bio-robust layer; and the second bio-robust coating is atomically sealed to the first bio-robust layer.

5. The nanochannel delivery device of claim 1 wherein the nanochannel is in direct fluid communication with the inlet microchannel and the outlet microchannel.

6. The nanochannel delivery device of claim 1 wherein the height of the etched nanochannel is less than 200 nm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIGS. 1-57 are schematic views of manufacturing processes according to exemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(2) As previously mentioned, in certain applications a nanochannel delivery device may be implanted into a human or animal body. It is therefore desirable that the materials exposed to bio-fluids be resistant to attack from those fluids. In certain applications, materials used in the construction of an NDD may not be resistant to bio-fluids.

(3) For example, bio-fluids may cause corrosion or erosion of silicon, silicon dioxide and silicon nitride. The NDD embodiments disclosed in the '233 and '937 Applications incorporate silicon nitride and silicon as the ceiling and floor of the nanochannels. While silicon nitride provides good tensile strength, it does not generally exhibit good corrosion/erosion resistance in certain applications in the human body (11,12)

(4) Therefore, it can be desirable to provide a coating of material that is bio-robust over a material that provides beneficial mechanical strength. As used herein, bio-robust materials include materials configured to withstand bio-fluids at body temperature (e.g., approximately 37 degrees Celsius) or elevated temperatures for extended periods of time. In specific embodiments, bio-robust materials maintain nanometer scale dimensions within 10 percent of their original dimensions over 1,000 days when exposed body fluids or equivalent at body temperature. These materials may include, for example, silicon carbide (SiC), tantalum oxide (Ta.sub.2O.sub.5), and other materials. Such materials may be deposited by chemical vapor deposition (CVD), atomic layer deposition (ALD), sputtering or by spin-on deposition, or a combination of these methods. In the exemplary embodiment described below, tantalum oxide is used to provide a bio-robust material in the inlet microchannels, while silicon carbide or Tantalum oxide/silicon carbide bilayer is used to provide a bio-robust material in other areas of the NDD that could be exposed to bio-fluids.

(5) Embodiments of the present disclosure do not require that the structural material of the NDD be both bio-robust and structurally adequate. Instead, materials that are not bio-robust, but structurally sound (e.g., possessing the required tensile, compressive, and/or shear strengths) can be coated or covered with bio-robust materials. The bio-protection of this structural material (with the weak bio-robustness) comes from the application of a second layer which is used as a lining, whose primary purpose is to provide bio-robustness. This lining layer material can then have a relaxed requirement of structural adequacy. This allows for use of a material with limited strength/stress but adequate bio-robustness with a material with limited bio-robustness, but with adequate strength/stress.

(6) Exemplary embodiments use a sacrificial channel material that can be selectively removed after the full device fabrication to create a nanochannel. Any material that can be wet-etched with a high selectivity with respect to other materials in the system can be used as the nanochannel material. The exemplary embodiment described below is based on Protocol 3 (Monolithically-Fabricated Capping Layer) disclosed in the '233 and '937 Applications.

(7) Referring initially to FIG. 1, a side section view of a silicon-on-insulator (SOI) wafer 100 comprises a lower silicon layer 103, an oxide layer 105 and an upper silicon layer 107. FIG. 2 illustrates a detailed view of a top portion of upper silicon layer 107 after a layer 109 of relatively thick bio-robust material has been deposited. In this exemplary embodiment, layer 109 comprises approximately 500 nm of silicon carbide deposited on upper silicon layer 107. As explained in more detail below, layer 109 serves as an etch landing material. Referring now to FIG. 3, a layer 111 of nanochannel material can be deposited on layer 109 to the desired thickness to form the nanochannel. In this embodiment, layer 111 comprises a layer of tungsten approximately 3 nm thick. Optionally, an additional bio-robust material can be laid under this sacrificial layer 111.

(8) Referring now to FIG. 4, a layer 113 of relatively thin bio-robust material can be deposited on layer 111. In this embodiment, layer 113 comprises a layer of silicon carbide approximately 30 nm thick, and acts as a line protect layer. Optionally, an additional bio-robust material can be laid under this material, and over the sacrificial layer 111. As shown in FIG. 5, a mask pattern can be applied and layers 111 and 113 etched and then cleaned. Referring now to FIG. 6, a relatively thick layer 117 of bio-robust material may be deposited as a chemical-mechanical planarization (CMP) stop. In certain embodiments, layer 117 may comprise silicon carbide. An additional layer 118 that can be used as a sacrificial hardmask, such as silicon oxide is deposited. FIG. 7, shows the same stack of components as FIG. 6, but oriented perpendicular from the view shown in FIG. 6.

(9) As shown in FIG. 8, the inlet microchannels can be formed by patterning with mask layer 115 and etching through the multiple deposited layers to silicon layer 107. As shown in FIG. 9, this etch is continued to stop at the oxide layer 105 and the wafer is cleaned. As shown in FIG. 10, a bio-robust layer 119 may be deposited on the wafer surface in order to coat the underlying silicon layer 107. In certain embodiments, bio-robust layer 119 may comprise ALD deposited material such as Ta.sub.2O.sub.5 since extreme conformality with the ability to cover a very high aspect ratio channel is desired.

(10) If the bio-robust material is incapable of resisting further process materials or conditions, additional sacrificial layers 114 and 116 can be deposited as shown in FIG. 11. Optionally, these materials can be TiN as layer 114 and ozone tetraethyl orthosilicate precursor deposited by a CVD technique, as layer 116, which deposits as a liner layer protecting the layer 119.

(11) As shown in FIG. 12, the excess oxide above the layer 114 is etched away using a dry plasma process, with the etch stopping on liner layer 114, while retaining the protection of layer 119 in the sidewalls of the inlet.

(12) The structure may then be filled with a material 121 with a high conformality, as shown in FIG. 13. In certain embodiments, material 121 may comprise silicon dioxide deposited by the ozone tetraethyl orthosilicate precursor through a CVD technique. In other embodiments, material 121 may comprise tungsten with a Titanium nitride or a Titanium/Titanium Nitride liner.

(13) As shown in FIG. 14, the entire overburden above the layer 118 is removed by chemical mechanical planarization (CMP)

(14) Referring now to FIG. 15 another mask 123 which is slightly larger than mask pattern 115 is patterned in resist. As shown in FIG. 16, material 121 in the vias is selectively etched with respect to material 118 by a plasma process. This is followed by another selective etch of layers 118, 117 and 111, stopping on the etch stop layer 109, as shown in FIG. 17. The etching depth can be controlled by adjusting the length of time of the etching process. In the embodiment shown, the etching stops in layer 109, below layer 111 (which is used to form the nanochannel) so that the nanochannel sidewalls are exposed. This creates inlet channels 122. Optionally, steps 16 and 17 can be combined into a single step by choosing an etch chemistry with appropriate selectivity. The remaining resist 123 can then be removed and the structure cleaned, as shown in FIG. 18. This is followed by removal of hardmask layer 118, as shown in FIG. 19.

(15) As shown in FIG. 20, a material 125 can then be deposited to fill inlet channels 122. In certain embodiments, material 125 may comprise tetraethyl orthosilicate oxide or TiN/tungsten. Referring now to FIG. 21, material 125 above the layer 117 may be removed by a CMP process, which terminates at layer 117. It is understood that the figures are not to scale, and that the top surface of layer 117 and material 125 may be generally planar or have a small topography.

(16) Referring now to FIG. 22, a layer 127 is deposited across the surface of wafer 100 to protect subsequently deposited layer 129 from bio-fluids in the inlet. In certain embodiments, layer 127 may comprise silicon carbide or an ALD Ta.sub.2O.sub.5 layer or a combination of the two. A layer 129 is then deposited on layer 127, as shown in FIG. 23. Layer 129 should provide structural integrity to the nanochannel device such that the aggregate stress of the overlayers above the nanochannels should be neutral or mildly tensile in nature (0-100 MPa), but need not be bio-robust. In certain embodiments, layer 129 may comprise silicon nitride.

(17) As shown in FIG. 24, a layer 131 can then be deposited on layer 129. In certain embodiments, layer 131 may comprise silicon carbide or an ALD Ta.sub.2O.sub.5 layer or a combination of the two. An oxide or a silicon nitride mask layer 133 can then be deposited onto layer 131, as shown in FIG. 25. Referring now to FIG. 26, outlet channels 135 can then be patterned on mask layer 133. As shown in FIG. 27, the wafer is etched through layers 133, 131, 129, 127 and stopping in layer 117. The photoresist material can then be stripped and wafer 100 cleaned as in FIG. 28.

(18) As shown in FIG. 29, a layer 132 can be deposited to form a thin layer within outlet channels 135. Layer 132 can therefore coat or cover the exposed portions of layer 129 (which possesses beneficial structural properties, but may not necessarily be bio-robust). In certain embodiments, this layer may comprise silicon carbide, or ALD Ta.sub.2O.sub.5 or a combination of the two. Referring now to FIG. 30, an additional etching step can be performed to extend outlet channels 135 through layer 117 and nanochannel layer 111 and stopping in layer 109 and the wafer cleaned. Referring now to FIG. 31, a protection layer 139 can be deposited onto layer 133 and into outlet channel 135.

(19) At this stage, wafer 100 can turned over, as shown in FIG. 32. A hardmask layer 140 is deposited on the backside as in FIG. 33. Macrochannels 141 are patterned with resist on this layer 140, with alignment to the frontside as shown in FIG. 34.

(20) Referring to FIG. 35, layer 140 is etched and the resist stripped and cleaned, to transfer the macrochannel pattern 141 to the hardmask. Optionally, this pattern transfer to hardmask is not needed and the macrochannel pattern is made in resist only.

(21) Macrochannels are then etched in layer 103, stopping at oxide layer 105, as shown in FIG. 36. Additional treatments to prepare a contamination free, smoother sidewall can be performed at this stage, for example, piranha and other cleans and KOH, SF.sub.6 or other silicon etches. Referring now to FIG. 37, oxide layer 105 can then be removed and macrochannels 141 extended to the device silicon layer 107. This process also removes the hardmask layer 140. An additional layer 143 of bio-robust material can then be deposited to cover the backside of the wafer 100, as shown in FIG. 38. This, again can be silicon carbide, Ta.sub.2O.sub.5, or a combination of the two.

(22) The wafer is then flipped over to face-up position, as shown in FIG. 39. As shown in FIG. 40, the frontside protection layer 139 is removed by appropriate means. Finally, as shown in FIG. 41, the sacrificial materials such as material 125, material 121, nanochannel layer 111, and protection layer 116 are removed. As shown in FIG. 41, nanochannel 110 (resulting from the removal of nanochannel layer 111) couples macrochannel 141 and inlet microchannel 122 with outlet microchannel 135.

(23) While one exemplary embodiment has been described above, other exemplary embodiments may comprise alternate processes or methods. For example, the processes described in FIGS. 29-30 may be substituted by those described in the following FIGS. 42-45. Processes described in FIGS. 29-30 are performed as a means to open the outlet side of the nanochannel, while still having a bio-robust material covering the sidewalls of the structural material. FIGS. 42-45 disclose an alternate method of accomplishing this, described by using a pattern to form a smaller via inside the original outlet microchannel (after the formation of the first outlet microchannel, followed by the Ta.sub.2O.sub.5 and/or silicon carbide deposition) and etch of this second outlet microchannel into the nanochannel, landing in the outlet etch stop material FIG. 42 describes a film stack similar to FIG. 29, that has been patterned with the outlet mask 135 and etched through materials 133, 131, 129, 127 and stopping in layer 117. Subsequently a layer 132 is deposited to cover the sidewalls of layer 129 as shown in FIG. 42. In certain embodiments, this layer can be silicon carbide or ALD Ta2O5 or combinations of the two. Resist is spun on this wafer and a second mask is exposed to pattern a smaller outlet within the larger outlet as layer 138 as shown in FIG. 43. The material from 132, any remaining material of 117 and the nanochannel material 111 is etched, stopping on the etch stop layer 109, and the residual resist removed as shown in FIG. 44. The resist is then stripped and wafer cleaned as shown in FIG. 45.

(24) Furthermore, the process described in FIGS. 15-21 are provided as a means to open the inlet side of the nanochannel, which would otherwise be covered by the liner material. While the method described in FIGS. 15-21 uses a second mask to etch out the liner, alternate methods may be employed to remove the liner at the interface with the inlet. For example, two such methods include: (1) performing a short isotropic etch to sputter away the sidewall containing the liner and (2)) removing the liner with a chemical, etched through the nanochannel, after the nanochannel has been removed.

(25) An alternate method to make the devices with materials protected by bio-robust layers is by changing the sequence of line and inlet formation process from line first, inlet second, to inlet first and line second. This can be accomplished, for example, in the manner described below.

(26) FIG. 46 has the wafer 100, with a thick silicon carbide layer 109, similar to the one in FIG. 2. A hardmask layer 118 is applied on to this surface as in FIG. 47. Referring now to FIG. 48, resist material 115 is spun on with an inlet pattern. The wafer is then subjected to a dry etch that stops at the buried oxide layer 105, to form inlets 204, as shown in FIG. 49. In FIG. 50, the resist 115 is stripped and the wafer cleaned.

(27) Referring now to FIG. 51, as in FIG. 10, a thin bio-robust material layer 119 is deposited. In certain embodiments, this could be ALD TaO. An additional sacrificial protection film 116, can be added as shown in FIG. 52. This structure is then coated with a film 121, with enough conformality to plug the inlets as shown in FIG. 53. In some embodiments, this layer can be TiN/W or silicon oxide deposited with Ozone and Tetraethylorthosilicate precursors. This structure is then subjected to CMP to remove all the over layers, stopping on layer 109 as shown in FIG. 54.

(28) Referring now to FIG. 55, a thin sacrificial material is deposited as layer 111, which can be sputtered tungsten. A bio-robust liner layer, which is not susceptible to oxidation can also be deposited below and above this layer if needed. A thin silicon carbide layer 113 is deposited on this surface as shown in FIG. 56. This layer can then be patterned with the line mask and the structure etched back to below the level of nanochannel layer 111, into the etchstop layer 109, as show in FIG. 57. The remaining processing steps continue from process in FIG. 23 of the previously-described process.

(29) In exemplary embodiments, it can be desirable to provide sealing of bio-robust materials so that the non-bio-robust materials are not exposed to bio-fluids. In specific embodiments, the bio-robust materials atomically seal to the non-bio-robust material that needs to be protected (without gaps for the bio-fluids to get through). In addition, the bio-robust layers seal to each other (e.g. sidewalls and top layers of channels). The bio-robust layer may also serve to adhere adjacent layers.

(30) In particular embodiments, atomic layer deposition (ALD) may be used because the layers are extremely conformal to residual surface topography in underlying layers. Examples of materials suitable for ALD include, but are not limited, to: Al.sub.2O.sub.3, Ta.sub.2O.sub.5, HfO.sub.2, HfSiO.sub.2, ZrO.sub.2, AlSiO.sub.2, TiN, Ti, TiAlN, AlN, HfN, TaN, TaCN, HfSiN, TiO. A table of additional materials that may be used for ALD is provided below.

(31) TABLE-US-00001 Compound class Examples II-VI compounds ZnS, ZnSe, ZnTe, ZnS.sub.1xSe.sub.x, CaS, SrS, BaS, SrS.sub.1xSe.sub.x, CdS, CdTe, MnTe, HgTe, Hg.sub.1xCd.sub.xTe, Cd.sub.1xMn.sub.xTe II-VI based thin-film ZnS:M (M = Mn, Tb, Tm), CaS:M electroluminescent (TFEL) (M = Eu, Ce, Tb, Pb), phosphors SrS:M (M = Ce, Tb, Pb, Mn, Cu) III-V compounds GaAs, AlAs, AlP, InP, GaP, InAs, Al.sub.xGa.sub.1xAs, Ga.sub.xIn.sub.1xAs, Ga.sub.xIn.sub.1xP Semiconductors/dielectric AlN, GaN, InN, SiN.sub.x nitrides Metallic nitrides TiN, TaN, Ta.sub.3N.sub.5, NbN, MoN Dielectric oxides Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5, Y.sub.2O.sub.3, MgO,CeO.sub.2, SiO.sub.2, La.sub.2O.sub.3, SrTiO.sub.3, BaTiO.sub.3 Transparent conductor oxides In.sub.2O.sub.3, In.sub.2O.sub.3:Sn, In.sub.2O.sub.3:F, In.sub.2O.sub.3:Zr, SnO.sub.2, SnO.sub.2:Sb, ZnO, Semiconductor oxides ZnO:Al, Ga.sub.2O.sub.3, MO, CoO.sub.x Superconductor oxides YBa.sub.2Cu.sub.3O.sub.7x Fluorides CaF.sub.2, SrF.sub.2, ZnF.sub.2

(32) Bio-robust materials may be deposited using only ALD, only CVD, or a combination of ALD and CVD. Additionally, the ALD and CVD materials can be deposited by thermally activated as well as by plasma or UV activated processes. In certain embodiments, the ALD layer can be a single layer or a multi-layer. In case of multi layers, one or more of these can be sacrificial liners that are etched away during the processing of the device leaving behind an underlayer that can still be protective in nature.

(33) Additionally, bio-robust materials may be deposited by sublimation, as in the case of Parylene in its various forms.

(34) While silicon nitride has been provided as an example of one non-bio-robust material, other materials include metals such as tungsten, copper, titanium, gold, platinum, ruthenium, aluminum, silver and other, as well as dielectrics. A partial list of dielectrics includes silicon and compounds of silicon such as oxides, nitrides, carbides, oxy nitrides, carbo-nitrides and oxy-carbides. Methyl silsequioxanes, hydrogen silsequioxanes and other organic silicates can be appropriately used. In addition plastics and polymeric materials such as PolyMethylMethAcrylate (PMMA), PolyCarbonate, PolyPropylene, Teflon and SU-8 can be used.

(35) All of the devices, systems and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the devices, systems and methods of this invention have been described in terms of particular embodiments, it will be apparent to those of skill in the art that variations may be applied to the devices, systems and/or methods in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

REFERENCES

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