Fabrication methods and structures for micro-reservoir devices

• US 7,413,846 B2
• Filed: 11/15/2004
• Issued: 08/19/2008
• Est. Priority Date: 11/15/2004
• Status: Active Grant

• Current Assignee: DARE MB Incorporated
• Original Assignee: MicroCHIPS Inc.
• Inventors: Santini, John T. Jr., Sheppard, Norman F. Jr., Maloney, John M., Uhland, Scott A., Sbiaa, Zouhair
• Primary Examiner(s): Huff; Mark F.
• Assistant Examiner(s): RAYMOND, BRITTANY L
• Application Number:
  US10/988,667
• Publication Number:
  US 20060105275A1
• Time in Patent Office: 1,373 Days
• Field of Search: 430/320, 430/318, 430/323, 430/322
• US Class Current: 430/320
• CPC Class Codes: A61K 9/0024 Solid, semi-solid or solidifying implants, which are implanted or injected in body tissue compositions for intravenous administration, normal injectable solutions or dispersions for, e.g. subcutaneous administration A61K9/0019; brain implants A61K9/0085; (coated) prostheses, catheters or stents A61L
• CPC Class Codes: A61K 9/0097 Micromachined devices; Microelectromechanical systems [MEMS]; Devices obtained by lithographic treatment of silicon; Devices comprising chips intradermal microneedle arrays A61K9/0021; MEMS in general B81B7/02
• CPC Class Codes: B01L 2200/12 Specific details about manufacturing devices
• CPC Class Codes: B01L 2300/0819 Microarrays; Biochips
• CPC Class Codes: B01L 2400/0677 phase change valves; Meltable, freezing, dissolvable plugs; Destructible barriers
• CPC Class Codes: B01L 3/50853 with covers or lids

Abstract

Methods are provided for making a multi-reservoir device comprising (i) patterning one or more photoresist layers on a substrate; (ii) depositing onto the substrate at least one metal layer by a sputtering process to form a plurality of reservoir caps and conductive traces; (iii) removing the photoresist layers using a liftoff process; (iv) forming a plurality of reservoirs in the substrate; (v) loading each reservoir with reservoir contents (such as a drug or sensor); and (vi) sealing each reservoir. Optionally, the reservoir cap comprises a first conductive metal layer coated with one or more protective noble metal films. To enhance the resistance of the substrate (e.g., a silicon substrate) to etching in vivo, the interior sidewalls of the reservoirs optionally can include a protective coating (e.g., gold, platinum, carbon, silicon carbide, silicon dioxide, and platinum silicide), or sidewalls comprising silicon can be doped with boron or another impurity.

Claims

1. A method for making a multi-reservoir device comprising:

patterning one or more photoresist layers on a substrate;

depositing onto the substrate at least one metal layer by physical vapor deposition;

forming a plurality of reservoir caps and conductive traces from the at least one metal layer by using the one or more photoresist layers in a liftoff process or wet chemical etching such that each reservoir cap is electrically connected to two conductive traces;

removing the one or more photoresist layers using a liftoff process;

forming a plurality of reservoirs in the substrate;

loading each reservoir with reservoir contents; and

sealing each reservoir.

2. The method of claim 1, wherein the reservoir cap comprises a first conductive metal layer coated with one or more protective noble metal film layers.

3. The method of claim 2, wherein the first conductive metal layer comprises titanium.

4. The method of claim 2, wherein the noble metal film comprises platinum.

5. The method of claim 2, wherein the thickness of the protective metal layer is less than about 20% of the thickness of the first conductive metal layer.

6. The method of claim 1, wherein the reservoirs comprise interior sidewalls and the method further includes forming at least one protective layer of material onto the sidewalls.

7. The method of claim 6, wherein the layer covering the sidewalls comprise a material selected from the group consisting of gold, platinum, diamond-like carbon, silicon carbide, silicon dioxide, and platinum silicide.

8. The method of claim 1, wherein the reservoirs comprise interior sidewalls comprising silicon doped with boron or another impurity to enhance the resistance of the silicon to etching under in vivo conditions.

9. The method of claim 1, further comprising bonding an additional substrate portion with through-substrate holes aligned with the reservoirs.

10. The method of claim 9, wherein the additional substrate portion comprises a silicon wafer or a glass wafer.

11. The method of claim 9, wherein the substrate and/or the additional substrate portion comprises silicon and the reservoirs and/or through holes are further treated with an isotropic silicon etchant to widen the hole or to smooth the surface of the hole.

12. The method of claim 9, wherein the additional substrate portion and the substrate are bonded together with an intermediate film.

13. The method of claim 12, wherein the intermediate film comprises a borosilicate glass.

14. The method of claim 9, wherein the additional substrate portion and the substrate are bonded by a process comprising anodic bonding, thermocompression bonding, or eutectic bonding.

15. The method of claim 1, comprising a bilayer liftoff process.

16. The method of claim 15, wherein the bilayer photoresist comprises an upper layer and a lower layer, wherein the lower layer is disposed on the substrate and the upper layer is disposed on the lower layer.

17. The method of claim 15, wherein the metal layer has no tags created by the sputtering and liftoff processes.

18. The method of claim 17, wherein the lower layer is laterally etched before the sputtering step, to create an overhang of the upper layer so that substantially no sputtered material is deposited on the sidewall of the lower layer.

19. The method of claim 15, wherein tags connected to the metal layer are formed by the sputtering and liftoff processes, and the tags are then removed.

20. The method of claim 19, wherein the tags are removed by a process comprising:

depositing a mask layer is deposited over the metal traces and/or reservoir caps, wherein the mask layer;

metal layer thickness ratio is from about 1;

5 to about 1;

1000; and

etching away the tags to yield metal traces and/or reservoir caps.

21. The method of claim 19, wherein the tags are removed by a sonication process.

26. The method of claim 1, wherein the reservoirs are micro-reservoirs.

27. The method of claim 1, wherein the reservoir contents comprises one or more drugs.

28. The method of claim 1, wherein the reservoir contents comprises one or more sensors or sensor components.

29. The method of claim 1, wherein the reservoir contents are hermetically scaled within the reservoirs.

30. The method of claim 1, wherein respective said conductive traces are connected to respective said reservoir caps and formed from the same one metal layer.

22. A microfabrication method comprising:

patterning a bilayer of photoresist on a substrate, wherein the bilayer photoresist comprises an upper layer and a lower layer, the lower layer being disposed on top of the substrate and the upper layer being disposed on top of the lower layer;

etching the lower layer away in select areas to form one or more bridges comprising areas of the upper layer over and spaced apart from the substrate, each said bridge having opposing first and second connection regions that are connected to the substrate;

depositing onto the substrate at least one metal layer by physical vapor deposition, wherein the one or more bridges provide a shielding effect to produce a metal film or patterned metal feature with a thickness variation within a single metal layer, without etching the metal layer;

forming a plurality of reservoir caps and conductive traces from the at least one metal layer by using the one or more photoresist layers in a liftoff process or wet chemical etching such that each reservoir cap is electrically connected to two conductive traces;

removing the bilayer photoresist layers using a liftoff process;

forming a plurality of reservoirs in the substrate;

loading each reservoir with reservoir contents; and

sealing each reservoir.

23. The method of claim 22, wherein the deposition method is selected from evaporation, sputtering, or ion beam deposition.

24. A method for making a multi-reservoir device comprising:

depositing a layer of a nitride material on a silicon substrate;

patterning the nitride layer with photoresist;

etching the nitride layer using an RIE process;

stripping off the photoresist;

anistropically etching the silicon substrate;

forming metal traces by depositing and patterning a first metal layer;

forming reservoir caps by depositing and patterning a second metal layer atop

portions of the first metal layer using a liftoff technique to form a structure;

applying a passivation layer onto the structure;

etching the passivation layer; and

etching the nitride layer from under the reservoir cap.

25. The method of claim 24, further comprising anodically bonding a patterned glass wafer to the substrate.

31. The method of claim 24, wherein said step of forming metal traces by depositing and patterning the first metal layer uses a liftoff technique.

32. The method of claim 24, wherein said step of forming metal traces by depositing and patterning the first metal layer uses a liquid etchant.