Patent Application
20050053849
The embodiments of various aspects of the invention relate generally to the formation of three-dimensional structures using electrochemical fabrication methods via a layer-by-layer build up of deposited materials and more particularly to the formation of beam-like structures that have a desired compliance.
A technique for forming three-dimensional structures (e.g. parts, components, devices, and the like) from a plurality of adhered layers was invented by Adam L. Cohen and is known as Electrochemical Fabrication. It is being commercially pursued by Microfabrica™ Inc. (formerly MEMGen® Corporation) of Burbank, Calif. under the name EFAB®. This technique was described in U.S. Pat. No. 6,027,630, issued on Feb. 22, 2000. This electrochemical deposition technique allows the selective deposition of a material using a unique masking technique that involves the use of a mask that includes patterned conformable material on a support structure that is independent of the substrate onto which plating will occur. When desiring to perform an electrodeposition using the mask, the conformable portion of the mask is brought into contact with a substrate while in the presence of a plating solution such that the contact of the conformable portion of the mask to the substrate inhibits deposition at selected locations. For convenience, these masks might be generically called conformable contact masks; the masking technique may be generically called a conformable contact mask plating process. More specifically, in the terminology of Microfabrica™ Inc. (formerly MEMGen® Corporation) of Burbank, Calif. such masks have come to be known as INSTANT MASKS™ and the process known as INSTANT MASKING or INSTANT MASK™ plating. Selective depositions using conformable contact mask plating may be used to form single layers of material or may be used to form multi-layer structures. The teachings of the '630 patent are hereby incorporated herein by reference as if set forth in full herein. Since the filing of the patent application that led to the above noted patent, various papers about conformable contact mask plating (i.e. INSTANT MASKING) and electrochemical fabrication have been published:
The disclosures of these nine publications are hereby incorporated herein by reference as if set forth in full herein.
The electrochemical deposition process may be carried out in a number of different ways as set forth in the above patent and publications. In one form, this process involves the execution of three separate operations during the formation of each layer of the structure that is to be formed:
After formation of the first layer, one or more additional layers may be formed adjacent to the immediately preceding layer and adhered to the smoothed surface of that preceding layer. These additional layers are formed by repeating the first through third operations one or more times wherein the formation of each subsequent layer treats the previously formed layers and the initial substrate as a new and thickening substrate.
Once the formation of all layers has been completed, at least a portion of at least one of the materials deposited is generally removed by an etching process to expose or release the three-dimensional structure that was intended to be formed.
The preferred method of performing the selective electrodeposition involved in the first operation is by conformable contact mask plating. In this type of plating, one or more conformable contact (CC) masks are first formed. The CC masks include a support structure onto which a patterned conformable dielectric material is adhered or formed. The conformable material for each mask is shaped in accordance with a particular cross-section of material to be plated. At least one CC mask is needed for each unique cross-sectional pattern that is to be plated.
The support for a CC mask is typically a plate-like structure formed of a metal that is to be selectively electroplated and from which material to be plated will be dissolved. In this typical approach, the support will act as an anode in an electroplating process. In an alternative approach, the support may instead be a porous or otherwise perforated material through which deposition material will pass during an electroplating operation on its way from a distal anode to a deposition surface. In either approach, it is possible for CC masks to share a common support, i.e. the patterns of conformable dielectric material for plating multiple layers of material may be located in different areas of a single support structure. When a single support structure contains multiple plating patterns, the entire structure is referred to as the CC mask while the individual plating masks may be referred to as “submasks”. In the present application such a distinction will be made only when relevant to a specific point being made.
In preparation for performing the selective deposition of the first operation, the conformable portion of the CC mask is placed in registration with and pressed against a selected portion of the substrate (or onto a previously formed layer or onto a previously deposited portion of a layer) on which deposition is to occur. The pressing together of the CC mask and substrate occur in such a way that all openings, in the conformable portions of the CC mask contain plating solution. The conformable material of the CC mask that contacts the substrate acts as a barrier to electrodeposition while the openings in the CC mask that are filled with electroplating solution act as pathways for transferring material from an anode (e.g. the CC mask support) to the non-contacted portions of the substrate (which act as a cathode during the plating operation) when an appropriate potential and/or current are supplied.
An example of a CC mask and CC mask plating are shown in
Another example of a CC mask and CC mask plating is shown in
Unlike through-mask plating, CC mask plating allows CC masks to be formed completely separate from the fabrication of the substrate on which plating is to occur (e.g. separate from a three-dimensional (3D) structure that is being formed). CC masks may be formed in a variety of ways, for example, a photolithographic process may be used. All masks can be generated simultaneously, prior to structure fabrication rather than during it. This separation makes possible a simple, low-cost, automated, self-contained, and internally-clean “desktop factory” that can be installed almost anywhere to fabricate 3D structures, leaving any required clean room processes, such as photolithography to be performed by service bureaus or the like.
An example of the electrochemical fabrication process discussed above is illustrated in
Various components of an exemplary manual electrochemical fabrication system 32 are shown in
The CC mask subsystem 36 shown in the lower portion of
The blanket deposition subsystem 38 is shown in the lower portion of
The planarization subsystem 40 is shown in the lower portion of
The '630 patent also teaches that other methods may be used to form contact masks (i.e. electroplating articles in the language of the '630 patent) which include applying masking composition selectively to a support by such processes as screen printing, stencil printing and inkjet printing.
The '630 patent also teaches that methods similar to those used in relief printing can also be used to fabricate electroplating articles (i.e. contact masks). A cited example of such a method includes: applying a liquid masking composition to a relief pattern, which might be produced by patterning a high aspect ratio photoresist such as AZ4620 or SU-8; pressing the relief pattern/masking composition structure against a support such that the masking composition adheres to the support; and removing the relief pattern. The formed electroplating article includes a support having a mask patterned with the inverse pattern of the relief pattern.
The '630 patent additionally teaches the creation of an electroplating article (i.e. a contact mask) by creating a relief pattern on a support by etching of the support, or applying a durable photoresist, e.g., SU-8; coating a flat, smooth sheet with a thin, uniform layer of liquid masking composition; stamping the support/resist against the coated sheet (i.e., like a stamp and inkpad) to quickly mate and unmate the support/resist and the masking composition (preferably the support and the sheet are kept parallel); and curing the liquid masking composition.
In addition to teaching the use of CC masks for electrodeposition purposes, the '630 patent also teaches that the CC masks may be placed against a substrate with the polarity of the voltage reversed and material may thereby be selectively removed from the substrate. It indicates that such removal processes can be used to selectively etch, engrave, and polish a substrate, e.g., a plaque.
The '630 patent further indicates that the electroplating methods and articles disclosed therein allow fabrication of devices from thin layers of materials such as, e.g., metals, polymers, ceramics, and semiconductor materials. It further indicates that although the electroplating embodiments described therein have been described with respect to the use of two metals, a variety of materials, e.g., polymers, ceramics and semiconductor materials, and any number of metals can be deposited either by the electroplating methods therein, or in separate processes that occur throughout the electroplating method. It indicates that a thin plating base can be deposited, e.g., by sputtering, over a deposit that is insufficiently conductive (e.g., an insulating layer) so as to enable subsequent electroplating. It also indicates that multiple support materials (i.e. sacrificial materials) can be included in the electroplated element allowing selective removal of the support materials.
Another method for forming microstructures from electroplated metals (i.e. using electrochemical fabrication techniques) is taught in U.S. Pat. No. 5,190,637 to Henry Guckel, entitled “Formation of Microstructures by Multiple Level Deep X-ray Lithography with Sacrificial Metal layers”. This patent teaches the formation of metal structure utilizing mask exposures. A first layer of a primary metal is electroplated onto an exposed plating base to fill a void in a photoresist, the photoresist is then removed and a secondary metal is electroplated over the first layer and over the plating base. The exposed surface of the secondary metal is then machined down to a height which exposes the first metal to produce a flat uniform surface extending across the both the primary and secondary metals. Formation of a second layer may then begin by applying a photoresist layer over the first layer and then repeating the process used to produce the first layer. The process is then repeated until the entire structure is formed and the secondary metal is removed by etching. The photoresist is formed over the plating base or previous layer by casting and the voids in the photoresist are formed by exposure of the photoresist through a patterned mask via X-rays or UV radiation.
It is an object of some aspects of the invention is to provide one or more beam-like structures having desired values of compliance which are greater than normally considered possible.
Other objects and advantages of various aspects of the invention will be apparent to those of skill in the art upon review of the teachings herein. The various aspects of the invention, set forth explicitly herein or otherwise ascertained from the teachings herein, may address one or more of the above objects alone or in combination, or alternatively they may address some other object of the invention that may be ascertained from the teachings herein. It is not necessarily intended that all objects be addressed by any single aspect of the invention even though that may be the case with regard to some aspects.
In a first aspect of the invention an elongated structure having a desired compliance, includes a structural material that is deposited configured with narrow regions separated by wider regions, wherein the widths of the regions are selected to yield desired mechanical properties.
In a second aspect of the invention a method of designing a structure, includes: designing the structure to one or more beam-like elements and to have a desired set of mechanical properties; comparing the dimensions of the designed structure with minimum feature size dimensions and determining that a width of at least one of the beam-like elements is narrower than a minimum feature size; modifying the configuration of at least one beam-like element that has a width narrower than the minimum feature size by, configuring portions of the one beam-like element to have a width greater than the minimum feature size and other portions of the beam-like element to have widths greater than the minimum feature size.
In a third aspect of the invention a method for producing a multi-layer structure having an elongated element having an effective compliance, includes: configuring a design of the elongated element to have portions that have widths less than a minimum feature size and portions having widths greater than the minimum feature size wherein a compliance of the structure is set at or below a desired amount; and producing the structure using masking operations and electrochemical deposition operations, where the formation of the masks or the use of the masks at least in part dictate the minimum feature size.
Further aspects of the invention will be understood by those of skill in the art upon reviewing the teachings herein. Other aspects of the invention may involve combinations of the above noted aspects of the invention and/or addition of various features of one or more embodiments. Other aspects of the invention may involve apparatus that can be used in implementing one or more of the above method aspects of the invention. These other aspects of the invention may provide various combinations of the aspects presented above as well as provide other configurations, structures, functional relationships, and processes that have not been specifically set forth above.
Various embodiments of various aspects of the invention are directed to formation of three-dimensional structures from materials some or all of which are to be electrodeposited. Some of these structures may be formed form a single layer of one or more deposited materials while others are formed from a plurality of layers of deposited materials (e.g. 2 or more layers, more preferably five or more layers, and most preferably ten or more layers). In some embodiments structures having features positioned with micron level precision and minimum features size on the order of tens of microns are to be formed. In other embodiments structures with less precise feature placement and/or larger minimum features may be formed. In still other embodiments, higher precision and smaller minimum feature sizes may be desirable.
Various embodiments of the invention may perform selective patterning operations using conformable contact masks and masking operations, proximity masks and masking operations (i.e. operations that use masks that at least partially selectively shield a substrate by their proximity to the substrate even if contact is not made), non-conformable masks and masking operations (i.e. masks and operations based on masks whose contact surfaces are not significantly conformable), and/or adhered masks and masking operations (masks and operations that use masks that are adhered to a substrate onto which selective deposition or etching is to occur as opposed to only being contacted to it). Adhered masks may be formed in a number of ways including (1) by application of a photoresist, selective exposure of the photoresist, and then development of the photoresist, (2) selective transfer of pre-patterned masking material, and/or (3) direct formation of masks from computer controlled depositions of material.
Various embodiments of the present invention are directed to the design of structures which include at least one narrow beam-like feature where the effective width of the beam-like feature is less than that generally considered to be reliably formable wherein the formation of the narrow feature is controlled by the selective deposition of material via a patterned mask (e.g. of the contact, proximity, or adhered type) or the selective etching via a patterned mask. In other words, various embodiments of the invention are directed to formation of structures having one or more features that have dimensions that are smaller than a minimum feature size, MFS. The MFS may vary based on the specifics of the formation process but is generally related to the ability to reliably form masks of desired patterning and to use those masks in depositing either a sacrificial or structural material or in etching a material in anticipation of filling created voids with a sacrificial or structural material. The MFS, for example, may be defined as the minimum width of a structure of defined length (e.g. 100-500 microns) that may be reliably formed (e.g. 90-99 times out of 100).
Various embodiments of the invention are directed to the formation of structures that, after formation and removal of sacrificial material, have narrow unsupported features where the width of the structure is at least in part based on it having a desired compliance (e.g. in the plane of the layer in a direction that has a component that is parallel to the width dimension (i.e. perpendicular to the elongated portion of the structure).
As noted above, in some embodiments the formation process involves the deposition of a sacrificial material as well as a structural material on a particular layer of a structure. Some embodiments allow a much narrower beam or similar structure to be successfully fabricated than is typically considered possible. As the beam width narrows the compliance of the beam increases most particularly within the plane of the layer and perpendicular to the length of the beam. However, for example, such beams may also be designed to achieve increased compliance perpendicular to the layer plane, or to achieve a required compliance in torsion.
In various embodiments of the invention the beam-like structures are formed with alternating lengths of narrow structural material and wider structural material. The lengths of narrow structural material are designed to produce most if not all of the compliance while the wider regions are designed such that they may result in reliable formation of themselves as well as of the intervening narrower regions. They are spaced within a distance of each other such that the narrower portions of the structure may also be formed reliably.
A first exemplary embodiment involves the selective deposition of sacrificial material using a patterned photoresist (or similar material) to define the pattern of openings for receiving a sacrificial material. After deposition of the sacrificial material, the resist is removed, and a deposition of structural material occurs. The deposition of structural material is typically performed in a blanket deposition manner but may be selectively deposited in some alternative embodiments. In embodiments where blanket deposition occurs, and even in some embodiments where selective deposition of structural material occurs, a planarization operation is performed to bring the net height of deposition to a desired level. In these embodiments, the pattern of structural material is initially manifest in the photoresist. For example, a beam that is to be formed out of nickel can be produced by patterning a beam in photoresist, plating sacrificial material (e.g., copper), stripping the resist, plating nickel, and then planarizing. For this process to work, the resist needs to adhere reasonably well to the substrate (or to a previously formed layer), since if it detaches and is washed away (e.g., during developing, processing related to developing, or plating) the beam will not be formed and the area intended to be occupied by resist and later by structural material will be occupied by sacrificial material. Similarly, the photoresist must be completely removed prior to the deposition of structural material, else structural material will not be deposited in at least some desired regions and the desired structure will not be properly formed.
It is observed that as features are designed smaller (e.g., as a beam is designed narrower) at some size, the resist (i.e. patterning material) will no longer remain reliably attached and the feature cannot be manufactured. Loss of the resist features may make it impossible to manufacture structures such as beams which are narrow enough, and thus sufficiently compliant, for the intended application.
According to some embodiments narrow beam structures are designed to include one or more wider “hold-down” features. These embodiments provide a method for designing and forming structures that can be manufactured with narrower elongated features and with greater compliance than would otherwise be possible, by providing ‘hold-down’ features which prevent loss of the narrower patterned resist structures.
The hold-downs of
The beams of
For a given length beam it is within the skill of the art to determine the width (e.g. empirically) that is required to reliably form a beam. Similarly for a given post or hold-down structure it is within the ability of those of skill in the art to determine the required dimensions for the structure so it will stay attached to a substrate or previously formed layer whether the substrate or previously formed layer comprises structural material or a sacrificial material that will eventually be removed.
If experimentation shows that sufficiently narrow hold-downs (e.g. similar to those of
In other embodiments the hold-down structures may take on shapes that are other than circular in nature. For example, they may have square or rectangular configurations or diamond shaped configurations. In still other embodiments the position or shape of the hold-downs need not be symmetric about the beam. For example, in some embodiments the hold-downs may be located on a single side of the beam or they may be located on alternating sides of the beam.
Beams made according to various embodiments of the invention can be arbitrarily tall (especially if made from multiple layers), thus making them extremely stiff in the direction perpendicular to the plane of the substrate and very compliant within the plane of the substrate.
In some embodiments, beams may be formed in combination with different structural elements that can be used to tailor the mechanical properties of the beam or to provide preferential bending locations and the like. In some embodiments, the beams may have portions with varying widths such that some portions provide less compliance than others. In other embodiments, as shown in
In other embodiments, the mechanical properties of the beam may be tailored by varying the size and spacings of the hold-down elements and even of the beam itself.
In other embodiments, beams may be formed in combination with different structural elements that can be used to set deflection limits or can be use to set controlled changes in compliance when certain deflection amounts occur. For example,
The patent applications and patents set forth below are hereby incorporated by reference herein as if set forth in full. The teachings in these incorporated applications can be combined with the teachings of the instant application in many ways: For example, enhanced methods of producing structures may be derived from some combinations of teachings, enhanced structures may be obtainable, enhanced apparatus may be derived, and the like.
Various other embodiments of the present invention exist. Some of these embodiments may be based on a combination of the teachings herein with various teachings incorporated herein by reference. Some embodiments may not use any blanket deposition process and/or they may not use a planarization process. Some embodiments may use selective deposition processes or blanket deposition processes on some layers that are not electrodeposition processes. Some embodiments may use electroplating deposition process, electrophoretic depositions process, electroless deposition processes, sputtering processes, spreading processes, and the like. Some embodiments, for example, may use nickel, gold, copper, tin, silver, zinc, solder as structural materials while other embodiments may use different materials. Some embodiments, for example, may use copper, tin, zinc, solder or other materials as sacrificial materials. Some embodiments may remove all sacrificial material while other embodiments may not. Some embodiments may use photoresist, polyimide, glass, ceramics, other polymers, and the like as dielectric structural materials.
In some embodiments, two materials may be deposited in association with individual layers but additional materials may be added to the overall structure by using different pairs of materials on different layers. For example, some layers may include copper and a dielectric while other layers may include nickel and copper. After the formation of the structure is completed, the copper may be removed as a sacrificial material which leaves behind a nickel and dielectric structure with hollowed out regions and/or a nickel, dielectric, and copper structure if copper is entrapped by regions of nickel and/or dielectric material. In other embodiments, more than two materials may be deposited in association with some layers.
It will be understood by those of skill in the art that additional operations may be used in variations of the above presented embodiments. These additional operations may, for example, perform cleaning functions (e.g. between the primary operations discussed above), they may perform activation functions, they may perform monitoring functions, and the like.
In view of the teachings herein, many further embodiments, alternatives in design and uses of the instant invention will be apparent to those of skill in the art. As such, it is not intended that the invention be limited to the particular illustrative embodiments, alternatives, and uses described above but instead that it be solely limited by the claims presented hereafter.
This application claims benefit of U.S. Provisional Patent Application No. 60/484,636 filed on Jul. 3, 2003. This referenced application is hereby incorporated herein by reference as if set forth in full.
| Number | Date | Country | |
|---|---|---|---|
| 60484636 | Jul 2003 | US |
