Method of making a corrugated deflection diaphragm

Abstract

A removable material is deposited or otherwise applied to a flat substrate surface in a pattern corresponding to desired corrugations in a membrane, e.g., a deflection diaphragm. The applied material serves as a scaffold for a polymeric material, which is applied thereover, and following cure or hardening, the polymeric material is removed to form a finished corrugated membrane.

Claims

1. A method of manufacturing a corrugated diaphragm suitable for use in a pump, the method comprising the steps of: applying a chemically removable layer onto a flat substrate, the removable layer having a relief pattern forming a positive mold therein; coating a membrane-forming layer comprising a hardenable polymer onto the positive mold in a liquid phase; and following hardening of the hardenable polymer, removing the removable layer to release the membrane-forming layer, thereby forming the corrugated diaphragm with corrugations corresponding to the relief pattern.

2. The method of claim 1, wherein the chemically removable layer is applied as a uniform coating onto the substrate and further comprising the step of patterning the uniformly applied coating to obtain the relief pattern.

3. The method of claim 2, wherein the removable layer is a photoresist and the patterning comprises (a) patternwise exposing the photoresist to actinic radiation and (b) subjecting the exposed photoresist to a developer.

4. The method of claim 3, wherein the photoresist is a positive photoresist.

5. The method of claim 3, wherein the photoresist is a negative photoresist.

6. The method of claim 1, wherein the polymer is parylene.

7. The method of claim 1, further comprising the step of patterning the membrane-forming layer by oxygen plasma etching using a shadow mask following hardening of the membrane-forming layer.

8. The method of claim 1, wherein the membrane-forming layer consists of a plurality of layers including at least one hardenable polymer layer and at least one metal layer.

9. The method of claim 1, wherein the substrate is silicon.

10. The method of claim 1, wherein the removing step comprises subjecting the removable layer to a solvent therefor.

11. The method of claim 1, further comprising applying an additional release layer onto the substrate prior to applying the membrane-forming layer.

12. The method of claim 11, wherein the additional release layer consists of a material different from the chemically removable layer.

13. The method of claim 12, wherein the releasing step comprises subjecting the additional release layer to a solvent therefor and subjecting the removable layer to a solvent therefor.

14. The method of claim 11, wherein the additional release layer consists of the same material as the chemically removable layer.

15. The method of claim 1, wherein the chemically removable layer is applied patternwise by deposition.

16. The method of claim 1, wherein the relief pattern comprises concentric circles.

17. The method of claim 1, wherein the relief pattern comprises concentric ovals.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, with an emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which:

(2) FIG. 1 schematically illustrates a representative embodiment of a fabrication method in accordance with the present invention.

(3) FIG. 2 illustrates the use of an additional release layer in the method shown in FIG. 1.

DETAILED DESCRIPTION

(4) Embodiments of the present invention utilize a pattern of a removable (e.g., chemically removable) material as a mold scaffold for fabrication of a corrugated deflection diaphragm. The diaphragm may be provided with different corrugation depths and lengths to accommodate the deflection requirements of a given electrolytic chamber.

(5) FIG. 1 shows a representative manufacturing process flow including the following steps:

(6) Step 1. Prepare a clean substrate 100 (e.g., a silicon wafer or other solid material with flat surface) by polishing the surface or otherwise ensuring its smoothness.

(7) Step 2. Apply a removable material on top of the substrate and pattern the material to produce a relief pattern that will serve as a positive mold scaffold 110. For example, the material may be applied directly (e.g., by pointwise deposition) in the form of the desired pattern, or may be applied to the entire surface and selectively removed.

(8) Step 3. Coat a polymer (e.g., parylene) or polymer-containing layer 120 on top of the positive mold scaffold 110 and cure the polymer or allow it to harden. The thickness of the polymer layer 120 can be equal to or greater than 5 m and less than or equal to 25 m. In some embodiments, a composite layer rather than a simple polymer is employed; for example, a succession of layers (e.g., parylene-metal-parylene, with a metal such as platinum) may be sequentially coated onto the scaffold. The total thickness of the polymer-containing layer can be equal to or greater than 4 m and less than or equal to 30 m. Each polymer layer of the composite layer can have a thickness equal to or greater than 2 m and less than or equal to 15 m. The metal layer of the composite layer can have a thickness equal to or greater than 0.05 m and less than or equal to 0.5 m. The polymer-containing layer may further comprise one or more sets of parylene-metal layers. The parylene layer interfaces with (i.e., presents a surface to) the drug reservoir. Either the parylene layer or metal layer may interface with the electrolysis reservoir. In embodiments where the metal layer interfaces with the electrolysis reservoir, the metal (i.e. platinum) may act as a recombination catalyst and reverse the electrolysis gas production reaction. The rate of recombination may be altered by controlling the amount of recombination catalyst exposed on the membrane surface facing the electrolysis reservoir.

(9) Step 4. Pattern the polymer layer by oxygen plasma etching using a shadow mask. The outer profile of each diaphragm is created and may include one or more tabs used for handling the diaphragm during subsequent processing steps. These tabs are later removed by mechanical or laser cutting to create the diaphragm profile to be integrated into the final product (i.e., drug pump). Additionally, this step separates one or more diaphragms from adjacent diaphragms created on a single silicon wafer.

(10) Step 5. Soak the coated substrate in a solvent for the removable material and release the finished polymeric membrane 130.

(11) Any suitable application method may be used in step 2, for example, pointwise deposition (e.g., using ink-jet equipment), photopatterning (e.g., photolithography), screen printing, stenciling, lamination, surface-wide coating (e.g., spin coating, wire-wound-rod coating, etc.) followed by selective removal (e.g., using a laser or a blade). Multiple coatings may be needed to achieve sufficient thickness, e.g., 100 m.

(12) In step 3, curing, if necessary, may be achieved in any fashion appropriate to the applied polymer, e.g., exposure to actinic radiation or simple drying. Some polymers, such as parylene, have no curing cycle.

(13) Similarly, in step 5, the solvent is chosen based on the applied material. For example, in the case of photoresist, the solvent may be isopropyl alcohol, photoresist developer, etc. Common photoresist compositions include Hoechst AZ 4620, Hoechst AZ 4562, Shipley 1400-17, Shipley 1400-27, Shipley 1400-37, and Shipley Microposit Developer.

(14) As illustrated in FIG. 2, an additional release layer 140 may be deposited onto the substrate 100 in order to shorten the soaking and releasing time in step 5. This release layer 140 may be the same material as the removable material 110 or a different material. For example, in the case of a photoresist layer 110, the additional layer 140 may be the same or different type of photoresist, and the layer 140 may be hard baked (i.e., baked at higher temperature or longer time) to prevent penetration by the layer 110.

(15) Alternatively, the layer 140 may be part of the removable layer 110 deposited in accordance with step 2 as described above. In this case, the additional release layer 140 can be formed in either of two ways. One way is simply to apply separate layers of the same material sequentially, the first layer constituting the additional release layer 140 and the second receiving the mold relief pattern. Another way is to use a single layer 110 and pattern it in a manner that affects only the upper portion of the layer thickness to create the pattern. For example, if the layer 110 is a photoresist, it may be patterned using positive photolithography, which involves patternwise exposure to actinic (e.g., UV) radiation followed by subjection to a chemical developer that removes the exposed regions of the photoresist. (In negative photolithography, the unexposed regions are removed.) In this case, exposure occurs at a fluence level that affects only the top portion of the layer thickness while leaving essentially intact a bottom portion that will constitute the additional release layer; the same effect can be achieved by exposing at a higher fluence but shortening the development time. For example, if 100 m of mold height is necessary to create the corrugations, the photoresist layer can be applied to a thickness of 120 m, leaving 20 m on the bottom of the corrugation structure to serve as the second release layer.

(16) In another alternative, the additional release layer is a material different from the photoresist. For example, the additional release layer may be SiO.sub.2 or a metal (e.g., aluminum, chromium, copper, gold, etc.). A SiO.sub.2 layer may be applied using thermal oxidation or a chemical vapor deposition process. A metal layer can be deposited by sputtering, thermal evaporation, or e-beam evaporation. The metal may also be applied to the substrate in sheet form, e.g., using an adhesive such as epoxy.

(17) If the additional release layer 140 is a material different from the overlying layer 110, it may require a different solvent to remove. For example, if the additional release layer 140 is SiO.sub.2, hydrofluoric acid (HF) may be used first to remove the SiO.sub.2 layer 140 followed by a chemical developer to remove, for example, a photoresist layer 110. If the layer is metale.g., aluminuma suitable etchant is used to etch away the aluminum layer. Polymers such as parylene are not affected by these solvents and etchants.

(18) Following removal of the additional release layer 140, the overlying structure is lifted off the substrate 100 and subjected to the action of a chemical developer to remove the layer 110. This will occur quickly due to the exposed lower surface.

(19) Certain embodiments of the present invention have been described above. It is, however, expressly noted that the present invention is not limited to those embodiments, but rather the intention is that additions and modifications to what was expressly described herein are also included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein were not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations were not made express herein, without departing from the spirit and scope of the invention. In fact, variations, modifications, and other implementations of what was described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention. As such, the invention is not to be defined only by the preceding illustrative description.