BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
The foregoing and other features and advantages of the present invention will be more readily appreciated as the same become better understood from the following detailed description when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 illustrates in cross-section a conventional fluidic channel or chamber structures;
FIG. 2 illustrates in cross-section an alternative approach to forming a conventional channel within a substrate;
FIGS. 3-5 illustrate the steps of the method in accordance with one embodiment of the invention for forming a microfluidic structure;
FIG. 6 illustrates one alternative embodiment of a microfluidic structure formed in accordance with the present invention;
FIG. 7 illustrates another embodiment of a microstructure formed in accordance with the present invention;
FIG. 8 illustrates a further embodiment of a microstructure formed in accordance with the present invention;
FIG. 9 illustrates stacked wafers and arrayed structures formed in accordance with the present invention;
FIG. 10 illustrates stacked structures and arrays formed in accordance with the present invention; and
FIG. 11 illustrates an alternative embodiment of a structure formed in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring next to FIGS. 3-5, illustrated therein is one embodiment of the invention that shows the steps of a method for forming a cavity. A substrate 42 is provided, preferably formed of silicon or other typical material used in forming microstructures or nanostructures. The substrate 42 has a first surface, in this case a top surface 44 on which is formed an optional layer of chip logic 46. It is to be understood that this chip logic can be formed on top of the substrate 42, or on top of and within the substrate 42, or solely within the substrate, as is well known. It is also to be understood that the chip logic layer 46 is optional and is not necessary to practice this embodiment of the invention. The chip logic layer 46 has a top surface 48 as shown in the side view of FIG. 3 on which is formed a first layer 50 of a first type of material. This first layer of material 50 will become the bottom of a cavity to be formed. In one aspect of this embodiment, the first layer of material 50 can be a film formed of metals, metal oxides, oxides, nitrides, deposited silicon films, oxynitrides, siliconcarbide, or an array of many materials. It can be deposited using one of many methods known to those skilled in the art, including chemical vapor deposition, electrodeposition, epitaxy, thermal oxidation, physical vapor deposition, and casting, among other methods.
The first layer 50 has an exposed surface 52 on which is formed patterned sacrificial material 54 of a selected shape. Ideally, the selected shape of the patterned sacrificial material 54 is the spatial opposite of a final cavity to be formed. This material 54 is ideally formed of “lost wax,” however other known sacrificial material can be used under appropriate conditions. The materials 54 has an exposed top surface 56 and sidewalls 58 that are substantially orthogonal to the exposed surface 52 of the first layer 50 and to the top surface 56.
Referring next to FIG. 4, shown here is a subsequent step in which a second layer of material 60 is formed over the first layer of material 50 and over the patterned sacrificial material 54 to cover the top surface 56 and sidewalls 58 of the patterned sacrificial material 54 such that it is enclosed between the first layer 50 and the second layer 60. Ideally, the second layer 60 functions as a liner for the subsequent chamber, channel, or cavity to be formed, and the second layer 60 is formed of the same type of material as the first layer 50 and, hence, the same process used to deposit or form the first layer 50 can be used here. At this point, the patterned sacrificial material 54 can be removed or a structural support layer 64 can be formed over a top surface 62 of the second layer 60 that extends to at least the portions of the second layer 60 that cover the sides 58 of the patterned sacrificial material 54. In a preferred embodiment, the patterned sacrificial material 54 is first removed and then the structural support layer 64 is added. The structural support layer 64 is preferably applied or formed by conventional methods on top of the second layer 60 and extends up to the level of the top of the second layer on the top side of the cavity 66.
With the removal of the sacrificial material 54, a cavity 66 is thus formed between the first and second layers 50, 60 and can remain completely enclosed as shown in FIG. 5. The structure 70 shown in FIG. 5 has the exposed surface 68 of the second layer 60 as the top surface of the structure 70. The particular structure 70 can be placed side by side with other structures 70, as shown in FIG. 6, to form a layered microfabricated structure 72 having multiple cavities 66. Alternatively, the layered microfabricated structure 72 can be formed on a unified substrate 42 or on separate substrates that are then placed together. Hence, the layered structure 72 can be formed of segments of microfabricated structure 70 or as a single unitary structure in which the layers are deposited across the entire substrate 42.
FIG. 7 illustrates another embodiment of the invention in which the microfabricated structure 70 has an opening 74 formed in the exposed surface 68 and through the second layer 60 to be in fluid communication with the cavity 66. In one embodiment, the cavity 66 can be formed as an elongate conduit having at least one and preferably two or more openings 74 to enable fluid, such as a gas or a liquid, to be conducted through the cavity 66. Microvalving may be used to control fluid flow into and out of the cavity.
FIG. 8 illustrates yet another embodiment of the invention in which a channel 76 is formed in the substrate and a subsequent opening 78 is formed through the chip logic layer 46 and the first layer 50 to be in fluid communication with the cavity 66. A combination of the embodiments shown in FIGS. 7 and 8 may also be formed, which is shown in FIG. 9. Here, a stacked composite structure 80 is constructed from a combination of the microfabricated structures 71 and 73 in which the microfabricated structure 73 having the triangular-shaped channel 76 formed in the substrate 42 is placed over the microfabricated structure 71 to be in fluid communication with the opening 74 and the cavity 66 thereof. This stacked composite structure 80 can be placed side by side with another stacked composite structure 80 to form an array structure 82.
Referring next to FIG. 10, shown therein is still yet another embodiment of the invention in which the structure 71 from FIG. 7 having the opening 74 in the top surface 68 has additional layers 84 of cavities 66 formed thereon. More particularly, a third layer of material 86 is formed over the second layer of material 60 and the structural support layer 64, after which patterned sacrificial material is placed over the third layer as described above with respect to FIGS. 3-5. A fourth layer 88 of material is formed over the third layer 86 and the patterned sacrificial material, and the patterned sacrificial material is then removed to form the cavity 66, as described above with respect to FIGS. 3-5. Ideally the first, second, third, and fourth layers are all formed of the same type material. Each cavity layer 84 has openings 90 formed therein through the third layer 86 and the fourth layer 88 to enable fluid communication between the layers of cavities 66. Here, this stacked cavity structure 92 can be placed adjacent another stacked array structure 92 to form a composite array structure 94.
Thus, the embodiments shown in FIGS. 7 and 8 show possible openings into the cavity 66 for fluid inlet and/or outlet, visual inspections, fluid pressure control, or any of several applications. The cavities 66 may be stacked in vertical orientation with interconnections via the openings 74, 76, 78, and 90 in any location. With the various arrays as illustrated in FIGS. 9 and 10, a honeycomb effect can be achieved with interconnections throughout.
While preferred embodiments of the invention have been illustrated and described, it is to be understood that various changes can be made therein without departing from the spirit and scope of the invention. For example, FIG. 11 shows the structure 70 from FIG. 5 having the structural support layer 64 extending further above the cavity 66 and the second layer 60. This provides additional topside support for the cavity 66, especially when additional structures are to be stacked, formed, or deposited thereon. Hence, the invention is to be limited only by the accompanying claims and the equivalents thereof.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
Patent Application
20070273728
