Enhanced methods for at least partial in situ release of sacrificial material from cavities or channels and/or sealing of etching holes during fabrication of multi-layer microscale or millimeter-scale complex three-dimensional structures

In a method for fabricating a multi-layer three-dimensional structure, comprising:

• (a) forming a first layer on a substrate comprising deposition of at least one sacrificial material and deposition of at least one structural material wherein the deposited sacrificial material and the deposited structural material are planarized to have a common height to set a boundary level for the first layer;
• (b) forming additional layers adjacent to and adhered to previously formed layers, wherein the formation of each additional layer comprises deposition of at least one sacrificial material and deposition of at least one structural material and wherein the sacrificial material and the structural material for each additional layer are planarized to have a common height to set a boundary level for each additional layer;
• and (c) after formation of the additional layers, etching at least one sacrificial material from a plurality of layers to release the three-dimensional structure from the sacrificial material, the improvement comprising:
• during the process of step (b), forming the structure to have an elongated passage having a passage length, a passage height, and a passage width and being at least partially free of solidified material along a portion of the passage height and passage width along a portion of the passage length prior to the etching of step (c).

In a method for fabricating a multi-layer three-dimensional structure, comprising:

• (a) forming a first layer on a substrate comprising deposition of at least one sacrificial material and deposition of at least one structural material wherein the deposited sacrificial material and the deposited structural material are planarized to have a common height to set a boundary level for the first layer;
• (b) forming additional layers adjacent to and adhered to previously formed layers, wherein the formation of each additional layer comprises deposition of at least one sacrificial material and deposition of at least one structural material and wherein the sacrificial material and the structural material for each additional layer are planarized to have a common height to set a boundary level for each additional layer;
• and (c) after formation of the additional layers, etching at least one sacrificial material from a plurality of layers to release the three-dimensional structure from the sacrificial material, the improvement comprising:
• partially forming the structure to comprise an elongated passage defined by structural material forming a bottom, sidewalls and an elongated upper access region defined by at least one opening through the structural material, wherein the at least one opening of the access region is defined by a width which relative to the access region as a whole, relative to a passage height, and relative to the passage width allows the at least one opening after, an etching step, to be closed by localized build up of deposited material without completely filling an at least partially cleared elongated passage with newly deposited solidified material, then
• i. selectively removing a sacrificial material from multiple layers from an interior of the elongated passage to form an at least partially cleared passage,
• ii. depositing sacrificial material to close the at least one opening of the access region while not completely refilling the at least partially cleared passage with solidified material
• iii. planarizing structural material and the sacrificial material closing the at least one opening of the access region;
• and
• iv. during formation of a subsequent layer, depositing a structural material to provide a structural material seal of the at least one closed opening of the access region.

In a method for fabricating a multi-layer three-dimensional structure, comprising:

• (a) forming a first layer on a substrate comprising deposition of at least one sacrificial material and deposition of at least one structural material wherein the deposited sacrificial material and the deposited structural material are planarized to have a common height to set a boundary level for the first layer;
• (b) forming additional layers adjacent to and adhered to previously formed layers, wherein the formation of each additional layer comprises deposition of at least one sacrificial material and deposition of at least one structural material and wherein the sacrificial material and the structural material for each additional layer are planarized to have a common height to set a boundary level for each additional layer;
• and (c) after formation of the additional layers, etching at least one sacrificial material from a plurality of layers to release the three-dimensional structure from the sacrificial material, the improvement comprising:
• partially forming the structure to comprise an elongated passage defined by structural material forming a bottom, sidewalls and an elongated upper access region defined by at least one opening through the structural material, wherein the at least one opening of the access region is defined by a width which relative to the access region as a whole, relative to a passage height, and relative to a passage width allows the at least one opening, after an etching step, to be closed by localized build up of deposited material without completely filling an at least partially cleared elongated passage, and then
• i. selectively removing a sacrificial material from multiple layers from an interior of the elongated passage to form an at least partially cleared passage;
• ii. depositing structural material to close the at least one opening of the access region while not completely refilling the at least partially cleared passage with solidified material;
• and
• iii. planarizing the structural material deposited to close the at least one opening of access region.