Fabrication of ultra-shallow channels for microfluidic devices and systems

Abstract

A method for etching an ultra-shallow channel includes using an etch process that is selective for one material to etch a different material in order to achieve a very precise channel depth in the different material. Channels as shallow as 10 nm can be fabricated in silicon with precision of 5 nm or better using the method. Stepped channels can be fabricated where each segment is a different depth, with the segments being between 10 nm and 1000 nm in depth. The method is applied to create a fluidic channel which includes a channel substrate to which is bonded a lid substrate to confine fluids to the fluidic channels so fabricated.

1 . An integrated fluidic channel system, comprising: a fluidic channel silicon substrate having a first surface and a second surface; said channel substrate defining a channel origination portion, a channel terminus portion, and a shallow or ultra-shallow channel extending between said channel origination portion and said channel terminus portion on at least said first surface, wherein said shallow or ultra-shallow channel includes at least a first segment that is between 10-1000 nm in depth; at least one of said channel origination portion, said channel terminus portion, and said channel being formed at least in part by reactive-ion etching; and a lid substrate having a first surface and a second surface, wherein said second surface of said lid substrate is attached to said first surface of said channel substrate to enclose said channel origination portion, said channel terminus portion, and said channel. 
   
   
       2 . The system of  claim 1 , wherein said lid substrate is of silicon. 
   
   
       3 . The system of  claim 1 , wherein said lid substrate is of borosilicate glass. 
   
   
       4 . The system of  claim 1 , wherein at least one of said channel origination portion and said channel terminus portion is at an edge of said channel substrate, and wherein said edge of said channel substrate is a surface that is at a perpendicular angle or an oblique angle to said first and said second surfaces of said channel substrate and that extends between said first and second surfaces of said channel substrate. 
   
   
       5 . The system of  claim 1 , further comprising an insulating layer over exposed surfaces of at least one of said channel origination portion, said channel terminus portion, and said channel. 
   
   
       6 . The system of  claim 5 , wherein said insulating layer is silicon oxide. 
   
   
       7 . The system of  claim 1 , wherein said channel substrate includes: (a) a plurality of channel origination portions on at least said first surface; (b) a plurality of channel terminus portions on at least said first surface; and (c) a plurality of shallow or ultra-shallow channels, each extending between one of said plurality of channel origination portions and said corresponding one of said plurality of channel terminus portions. 
   
   
       8 . The system of  claim 1 , wherein said channel substrate further includes: (a) an entrance opening on said second surface of said channel substrate; (b) an exit opening on said second surface of said channel substrate; (c) a channel extending between said entrance opening and said channel origination portion on said first surface of said channel substrate such that said entrance opening is in fluid communication with said channel origination portion; and (d) a second channel extending between said exit opening and said channel terminus portion on said first surface of said channel substrate such that said exit opening is in fluid communication with said channel terminus portion. 
   
   
       9 . The system of  claim 8 , further comprising an insulating layer over exposed surfaces of at least one of said channels. 
   
   
       10 . The system of  claim 9 , wherein said insulating layer is silicon oxide. 
   
   
       11 . The system of  claim 1 , wherein said channel substrate further includes (a) an entrance opening on said second surface of said channel substrate, and (b) a channel extending between said entrance opening and said channel origination portion on said first surface of said channel substrate such that said entrance opening is in fluid communication with said channel origination portion; and wherein said lid substrate further includes (a) an exit opening on said first surface of said lid substrate; and (b) a channel extending between said exit opening and said channel terminus portion on said first surface of said channel substrate such that said exit opening is in fluid communication with said channel terminus portion. 
   
   
       12 . The system of  claim 11 , wherein said lid substrate is of silicon. 
   
   
       13 . The system of  claim 11 , wherein said lid substrate is of borosilicate glass. 
   
   
       14 . The system of  claim 11 , further comprising an insulating layer over exposed surfaces of at least one of said channels. 
   
   
       15 . The system of  claim 14 , wherein said insulating layer is silicon oxide. 
   
   
       16 . The system of  claim 1 , wherein said channel substrate further includes: (a) an exit opening on said second surface of said channel substrate, and (b) a channel extending between said exit opening and said channel terminus portion on said first surface of said channel substrate such that said exit opening is in fluid communication with said channel terminus portion; and wherein said lid substrate further includes: (a) an entrance opening on said first surface of said lid substrate; and (b) a channel extending between said entrance opening and said channel origination portion on said first surface of said channel substrate such that said entrance opening is in fluid communication with said channel origination portion. 
   
   
       17 . The system of  claim 16 , wherein said lid substrate is of silicon. 
   
   
       18 . The system of  claim 16 , wherein said lid substrate is of borosilicate glass. 
   
   
       19 . The system of  claim 16 , further comprising an insulating layer over exposed surfaces of at least one of said channels. 
   
   
       20 . The system of  claim 19 , wherein said insulating layer is silicon oxide. 
   
   
       21 . The system of  claim 1 , wherein said lid substrate further includes: (a) an entrance opening on said first surface of said lid substrate; (b) an exit opening on said first surface of said lid substrate; (c) a channel extending between said entrance opening and said channel origination portion on said first surface of said channel substrate such that said entrance opening is in fluid communication with said channel origination portion; and (d) a channel extending between said exit opening and said channel terminus portion on said first surface of said channel substrate such that said exit opening is in fluid communication with said channel terminus portion. 
   
   
       22 . The system of  claim 21 , wherein said lid substrate is of silicon. 
   
   
       23 . The system of  claim 21 , wherein said lid substrate is of borosilicate glass. 
   
   
       24 . The system of  claim 21 , further comprising an insulating layer over exposed surfaces of at least one of said channels. 
   
   
       25 . The system of  claim 24 , wherein said insulating layer is silicon oxide. 
   
   
       26 . The system of  claim 1 , wherein said shallow or ultra-shallow channel includes at least a second segment, wherein said at least second segment is of a greater or lesser depth than said at least first segment. 
   
   
       27 . The system of  claim 26 , wherein said at least second segment is of a depth greater than 1000 nm. 
   
   
       28 . The system of  claim 1 , wherein said shallow or ultra-shallow channel includes at least a second segment, wherein said at least second segment is of a greater or lesser width than said at least first segment. 
   
   
       29 . The system of  claim 28 , wherein at least second segment is of a depth greater than 1000 nm. 
   
   
       30 . The system of  claim 1 , wherein said channel substrate further includes: a second channel origination portion, a second channel terminus portion, and a second shallow or ultra-shallow channel extending between said second channel origination portion and said second channel terminus portion on said second surface of said channel substrate; and a third substrate having a first and a second surface, wherein said second surface of said third substrate is attached to said second surface of said channel substrate to enclose said second channel origination portion, said second channel terminus portion, and said second channel. 
   
   
       31 . The system of  claim 30 , wherein said channel substrate further includes: (a) a second plurality of channel originations on said second surface; (b) a second plurality of channel terminus portions on said second surface; and (c) a second plurality of shallow or ultra-shallow channels, each extending between one of said second plurality of channel origination portions and said corresponding one of said second plurality of channel terminus portions. 
   
   
       32 . The system of  claim 30 , wherein said third substrate is of silicon. 
   
   
       33 . The system of  claim 30 , wherein said lid substrate is of borosilicate glass. 
   
   
       34 . The system of  claim 30 , wherein said channel substrate further includes: at least one channel extending between said channel origination portion or said channel terminus portion on said first surface of said channel substrate and said second channel origination portion or said second channel terminus portion on said second surface of said channel substrate, such that said shallow or ultra-shallow channel on said first surface is in fluid communication with said second shallow or ultra-shallow channel on said second surface. 
   
   
       35 . The system of  claim 31 , wherein said channel substrate further includes: a third plurality of channels, each extending between one of said channel origination portions or said channel terminus portions on said first surface of said channel substrate and a corresponding one of said second channel origination portions or said second channel terminus portions on said second surface of said channel substrate, such that each said shallow or ultra-shallow channel on said first surface is in fluid communication with its corresponding one of said shallow or ultra-shallow second channel on said second surface. 
   
   
       36 . The system of  claim 1 , wherein said lid substrate is of a material that is transmissive to at least a bandwidth of designated wavelengths of electromagnetic energy. 
   
   
       37 . The system of  claim 36 , wherein said lid substrate provides optical access for said electromagnetic energy to at least part of said shallow or ultra-shallow channel. 
   
   
       38 . The system of  claim 37 , wherein said lid substrate is effective for permitting fluid constituents residing statically or transiently in said channel to be excited, stimulated, or altered through absorption of said electromagnetic energy. 
   
   
       39 . The system of  claim 37 , wherein said lid substrate is effective for permitting at least a bandwidth of designated wavelengths of electromagnetic energy that are reflected from or emitted by fluid constituents residing statically or transiently in said channel to be detected, sensed, or measured by means integral or external to said system. 
   
   
       40 . The system of  claim 37 , further comprising at least one of: generation means for generating designated wavelengths of electromagnetic energy, said generation means being integral to at least one of said channel substrate and said lid substrate; and detection means for detecting, sensing, or measuring said designated wavelengths of electromagnetic energy, said detection means being integral to at least one of said channel substrate and said lid substrate. 
   
   
       41 . The system of  claim 1 , wherein said lid substrate is anodically bonded to said channel substrate.