Flow cells and methods for making the same
A metal film is formed over a resin layer including a plurality of multi-depth depressions (MDP) separated by interstitial regions, each MDP including a deep portion and an adjacent shallow portion. A sacrificial layer is formed over the metal film. The sacrificial layer and metal film are sequentially dry etched to expose a resin layer surface at the shallow portion and interstitial regions. Resin layer portions are removed i) at the shallow portion to form a depression region having a surface directly adjacent to a surface at the deep portion and ii) at the interstitial regions to form new interstitial regions surrounding the deep portion and the depression region. First functionalized layer is deposited over the metal film, depression region, and new interstitial regions. The metal film is removed from the deep portion. Second functionalized layer is deposited over the surface at the deep portion. New interstitial regions are polished.
1 . A method, comprising:
forming a metal film on a portion of a sidewall of each of a plurality of multi-depth depressions defined in a resin layer and separated by interstitial regions, wherein each multi-depth depression includes a deep portion and a shallow portion adjacent to the deep portion and wherein at least some of a bottom surface of each multi-depth depression is free of the metal film;
depositing a first functionalized layer over each of the multi-depth depressions and the interstitial regions;
patterning the first functionalized layer, whereby a portion of the first functionalized layer in the deep portion is covered by a region of a sacrificial layer and portions of the first functionalized layer in the shallow portion, over the metal film, and over the interstitial regions are removed;
depositing a second functionalized layer over the interstitial regions, over the metal film, over the region of the sacrificial layer, and in the shallow portion;
lifting off the region of the sacrificial layer, thereby exposing the portion of the first functionalized layer;
wet etching the metal film, thereby removing the second functionalized layer positioned over the metal film; and
polishing the interstitial regions, whereby the portion of the first functionalized layer in the deep portion and the second functionalized layer in the shallow portion remain intact.
2 . The method as defined in claim 1 , wherein forming the metal film on the portion of the sidewall of each multi-depth depression involves:
depositing an other sacrificial layer on the resin layer;
curing the other sacrificial layer;
etching back the other sacrificial layer to expose the portion of the sidewall of each multi-depth depression;
using a directional coating method, applying a metal material on the interstitial regions, on the portion of the sidewall of each multi-depth depression, and on the other sacrificial layer;
using anisotropic etching to remove the metal material from the interstitial regions and from the other sacrificial layer, whereby a portion of the metal material remains on the portion of the sidewall in each multi-depth depression; and
removing the other sacrificial layer using an organic solvent.
3 . The method as defined in claim 1 , wherein forming the metal film on the portion of the sidewall of each multi-depth depression involves:
conformally coating a metal material on the resin layer using sputtering; and
using anisotropic etching to remove the metal material from the interstitial regions and from the bottom surface of each multi-depth depression, whereby a portion of the metal material remains on the portion of the sidewall in each multi-depth depression.
4 . The method as defined in claim 1 , wherein patterning the first functionalized layer involves:
depositing a gel material;
curing the gel material to form the first functionalized layer;
applying the sacrificial layer over the first functionalized layer; and
dry etching the sacrificial layer and the portions of the first functionalized layer in the shallow portion and over the interstitial regions.
5 . The method as defined in claim 4 wherein the dry etching is a timed dry etch involving a reactive ion etch with 10% CF 4 and 90% O 2 or a 100% O 2 plasma etch.
6 . The method as defined in claim 1 , wherein:
the metal film is an aluminum metal film; and
wet etching utilizes nitric acid or potassium hydroxide.
7 . The method as defined in claim 1 , wherein:
the metal film is a copper metal film; and
wet etching utilizes FeCl 3 .
8 . The method as defined in claim 1 , wherein:
the metal film is selected from the group consisting of a copper metal film, a gold metal film, and a silver metal film; and
wet etching utilizes iodine or an iodide solution.
9 . The method as defined in claim 1 , wherein:
the metal film is a silicon metal film; and
wet etching utilizes potassium hydroxide.