NANOPORE FLOW CELLS AND METHODS OF FABRICATION
Nanopore flow cells and methods of manufacturing thereof are provided herein. In one embodiment a method of forming a flow cell includes forming a multilayer stack on a first substrate, e.g., a monocrystalline silicon substrate, before transferring the multilayer stack to a second substrate, e.g., a glass substrate. Here, the multilayer stack features a membrane layer, having a first opening formed therethrough, where the membrane layer is disposed on the first substrate, and a material layer is disposed on the membrane layer. The method further includes patterning the second substrate to form a second opening therein and bonding the patterned surface of the second substrate to a surface of the multilayer stack. The method further includes thinning the first substrate and thinning the second substrate. Here, the second substrate is thinned to where the second opening is disposed therethrough. The method further includes removing the thinned first substrate and at least portions of the material layer to expose opposite surfaces of the membrane layer.
This Application is a Divisional of U.S. application Ser. No. 16/573,540, filed on Sep. 17, 2019, which issues on Feb. 15, 2022 as U.S. Pat. No. 11,249,067, which claims the benefit of U.S. Provisional Application 62/752,045 filed on Oct. 29, 2018, each of which are incorporated by reference in their entirety.
BACKGROUND FieldEmbodiments herein relate to flow cells to be used with solid-state nanopore sensors and methods of manufacturing thereof.
Description of the Related ArtSolid-state nanopore sensors have emerged as a low-cost, highly mobile, and rapid processing biopolymer, e.g., DNA or RNA, sequencing technology. Solid-state nanopore sequencing of a biopolymer strand comprises translocating the biopolymer strand through a nanoscale sized opening having a diameter between about 0.1 nm and about 100 nm, i.e., a nanopore. Typically, the nanopore is disposed through a membrane layer which separates two conductive fluid reservoirs. The biopolymer strand to be sequenced, e.g., a characteristically negatively charged DNA or RNA strand, is introduced into one of the two conductive fluid reservoirs and is then drawn through the nanopore by providing an electric potential therebetween. As the biopolymer strand travels through the nanopore the different monomer units thereof, e.g., protein bases of a DNA or RNA strand, occlude different percentages of the nanopore thus changing the ionic current flow therethrough. The resulting current signal pattern can be used to determine the sequence of monomer units in the biopolymer strand, such as the sequence of proteins in a DNA or RNA strand.
Often, the membrane layer and the nanopore disposed therethrough are fabricated on a monocrystalline silicon substrate which together therewith forms a nanopore flow cell. The monocrystalline silicon substrate is typically the same or similar to substrates used in the manufacturing of semiconductor devices. Using the same or similar substrate to those used in the manufacture of semiconductor devices facilitates fabrication of the nanopore flow cell using commercially available semiconductor device manufacturing equipment and methods.
Typically, a membrane layer is deposited onto a front side surface of a silicon substrate and the nanopore opening is formed through the membrane layer, but not through the silicon substrate, using a photolithography patterning and etch processing sequence. A surface of the membrane layer disposed proximate to the silicon substrate is then exposed by etching an opening into a backside surface of the silicon substrate. Typically, the opening in the backside surface of the silicon substrate is formed by exposing the backside surface of the substrate to a wet or aqueous silicon etchant, such as KOH, through a patterned mask disposed thereon. A typical silicon substrate will need to be exposed to the silicon etchant for between 9 and 13 hours to anisotropically etch through the thickness thereof. This long etch time undesirably increases the cycle time, and thus the cost, of forming the nanopore flow cell. Further, charges accumulated in the monocrystalline substrate used to support the membrane layer during high frequency nucleotide detection in a conventional nanopore flow cell undesirably increase background noise in the current signal. This undesirable background noise reduces the detection resolution of the nanopore sensor or flow cell.
Accordingly, what is needed in the art are improved methods of forming a nanopore flow cell for use in a solid-state nanopore sensor and improved nanopore flow cells formed therefrom.
SUMMARYEmbodiments of the present disclosure provide devices, e.g., nanopore flow cells, which may be used in a solid-state nanopore sensor, and methods of manufacturing thereof.
In one embodiment a method of forming a flow cell includes forming a multilayer stack on a first substrate, e.g., a monocrystalline silicon substrate, before transferring the multilayer stack to a second substrate, e.g., a glass substrate. Here, the multilayer stack features a membrane layer, having a first opening formed therethrough, where the membrane layer is disposed on the first substrate, and a material layer is disposed on the membrane layer. The method further includes patterning the second substrate to form a second opening therein and bonding the patterned surface of the second substrate to a surface of the multilayer stack. The method further includes thinning the first substrate. The method further includes removing the thinned first substrate and at least portions of the first and second material layers to expose opposite surfaces of the membrane layer. In some embodiments, the second opening is disposed through the second substrate. In other embodiments, the method includes thinning the second substrate to where the second opening is disposed therethrough. Here, the second substrate may be thinned before or after the patterned surface thereof is bonded to the surface of the multilayer stack.
In another embodiment, a method of forming a flow cell includes forming a multilayer stack on a first substrate, the multilayer stack comprising a membrane layer interposed between a first material layer and a second material layer, where the membrane layer features a first opening formed therethrough. The method further includes patterning a surface of a second substrate to form a second opening therein, bonding the patterned surface of the second substrate to a first surface of the multilayer stack, and removing the first substrate from the multilayer stack to expose a second surface of the multilayer stack opposite of the first surface. The method further includes patterning a surface of a third substrate to form a third opening therein, bonding the patterned surface of the third substrate to the second surface of the multilayer stack, and thinning the second substrate and the third substrate to where the second opening and the third openings are respectively disposed therethrough. The method further includes removing at least portions of the first and second material layers to expose opposite surfaces of the membrane layer.
In another embodiment a nanopore flow cell features a glass substrate having an opening formed therethrough and a membrane layer disposed on the glass substrate. The membrane layer features a single nanopore disposed therethrough. The single nanopore is located in a portion of the membrane layer which spans the opening formed through the glass substrate.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one aspect may be beneficially incorporated in other aspects without further recitation.
DETAILED DESCRIPTIONEmbodiments of the present disclosure provide devices, e.g., nanopore flow cells, which may be used in a solid-state nanopore sensor, and methods of manufacturing the same. The methods described herein generally include forming a patterned multilayer stack on a sacrificial monocrystalline silicon substrate before transferring the patterned multilayer stack to a host substrate. The patterned multilayer stack typically features a membrane layer having a nanoscale opening disposed therethrough. The host substrate is typically formed of a dielectric glass material. Thus, the nanopore flow cells formed herein are substantially free of monocrystalline silicon materials. Beneficially, the glass material of the host substrate eliminates or substantially reduces background noise levels associated with solid-state nanopore flow cells comprising a monocrystalline silicon substrate.
Here, the ionic current flow draws a characteristically negatively charged DNA or RNA biopolymer strand, e.g. one of the biopolymer strands 107 from the first reservoir 102 through the nanopore 108 and into the second reservoir 103. As the biopolymer strand 107 is drawn through the nanopore 108 the monomer units thereof sequentially occlude the nanopore 108 causing a change in the ionic current flow therethrough. Typically, the change in the ionic current flow corresponds to a characteristic, such as a dimension or charge, of the monomer unit simultaneously passing through the nanopore 108. Here, the ionic current flow and changes in the ionic current flow are measured using an ion current sensor, such as a pico ammeter 110.
At activity 301 the method 300 includes forming a multilayer stack on a first substrate 401, shown in
Here, forming the multilayer stack includes depositing the first material layer 402 onto the first substrate 401, depositing a membrane layer 403 over the first material layer 402, and patterning the membrane layer 403 to form a first opening 404 therethrough, such as shown in
Typically, the first material layer 402 is formed of a dielectric material, such as a silicon oxide (SixOy), for example, SiO2. Here, the first material layer 402 is deposited to a thickness T(2) of more than about 10 nm, such as between about 10 nm and about 500 nm, between about 10 nm and 400 nm, between about 10 nm and about 300 nm, for example between about 10 nm and about 200 nm. In other embodiments, the first material layer 402 is deposited to a thickness T(2) of more than about 1 μm, such as more than about 2 μm, or more than about 3 μm, for example between about 4 μm and about 6 μm.
The membrane layer 403 is formed of a dielectric material which is different from the dielectric material(s) used to form the first and second material layers 402, 405. For example, in some embodiments the membrane layer 403 is formed of a silicon nitride or silicon oxynitride material, such as SixNy or SiOxNy. Typically, the membrane layer 403 is deposited to a thickness T(3) of about 500 nm or less, such as about 400 nm or less, about 300 nm or less, about 200 nm or less, about 100 nm or less, or about 50 nm or less, for example between about 0.1 nm and about 100 nm or between about 1 nm and about 100 nm.
The first opening 404 is formed to extend through the membrane layer 403 and to have a diameter D of less than about 100 nm, such as less than about 50 nm, or between about 0.1 nm and about 100 nm, for example between about 1 nm and about 100 nm, or between about 0.1 nm and about 50 nm. Here, the first opening 404 is formed using one or a combination of suitable lithography and material etching patterning methods. Typically, suitable lithography methods include nanoimprint lithography, directed self-assembly, photolithography, ArF laser immersion lithography, deep UV lithography, or combinations thereof.
Here, the second material layer 405, deposited over the membrane layer 403, is formed of a dielectric material which may be the same or different from the dielectric material used to form the first material layer 402. In some embodiments, the second material layer 405 is deposited to a thickness T(4) of between about 10 nm, such as between about 10 nm and about 500 nm, between about 10 nm and 400 nm, between about 10 nm and about 300 nm, for example between about 10 nm and about 200 nm. Herein, the layers of the multilayer stack may be formed using any suitable deposition method. For example, in some embodiments, the layers of the multilayer stack are deposited using one, or a combination, of chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods.
At activity 302 the method 300 includes patterning a surface of a second substrate 407 to form an opening therein, here the second opening 409 shown in
Here, the second substrate 407 is formed, for example, of a non-crystalline amorphous solid, i.e., glass, such as a transparent silica-based glass material, for example, a fused silica, i.e., an amorphous quartz material, or a borosilicate glass material. In some embodiments, the second substrate 407 has an opaque material layer 408, for example, an amorphous silicon layer deposited on a backside surface thereof. The backside surface of the second substrate 407 is opposite of the surface to be patterned, here the front side surface into which the second opening 409 is formed. When used, the opaque material layer 408 typically has a thickness T(6) of about 20 nm or more, for example, about 100 nm or more. The opaque material layer 408 facilitates the detection of an otherwise optically transparent substrate, according to some embodiments, by optical sensors of conventional semiconductor device manufacturing equipment.
Here, the second opening 409 is formed to extend from a surface of the second substrate 407, here the patterned surface, to a depth H of between about 100 μm or more and less than the thickness T(5) of the second substrate 407. For example, in some embodiments, the depth H of the second opening 409 extends between about 100 μm and about 600 μm, or between about 200 μm and about 400 μm, from the front side surface of the second substrate 407. In some other embodiments, such as in embodiments where the thickness of the second substrate 407 is less than about 400 μm the second opening 409 is formed to extend through the thickness of thereof.
Here, the second opening 409 is formed to have a width W(1) of between about 1 μm and about 20 μm, such as between about 1 μm and about 15 μm, between about 5 μm and about 15 μm, or between about 5 μm and about 10 μm. The second opening 409 may be formed using any suitable combination of photolithography and material etching patterning methods.
At activity 303 the method 300 includes bonding the patterned surface of the second substrate 407 to an exposed surface of the multilayer stack disposed on the first substrate 401, such as shown in
Herein, bonding the patterned surface of the second substrate 407 to the exposed surface of the multilayer stack includes aligning the second opening 409 407 with the first opening 404. When the first and second substrates 401, 407 are properly aligned, the first opening 404 and the second opening 409 in the resulting nanopore flow cell will be in fluid communication, e.g., a portion of the membrane layer 403 having the first opening 404 formed therethrough will span the second opening 409 formed in the second substrate 407.
At activity 304 the method 300 includes thinning the first substrate 401. Thinning the first substrate 401 includes any one or combination of grinding, lapping, chemical mechanical planarization (CMP), etching, or cleaving methods which may be used to achieve a desired thickness T(7) (shown in
At activity 305, the method 300 includes thinning the second substrate 407 using any one or combination of grinding, lapping, CMP, or etching methods to achieve a desired thickness T(8) (shown in
At activity 306, the method 300 includes removing the thinned first substrate 401 and at least portions of the first and second material layers 402, 405 to expose opposite surfaces of the membrane layer 403 spanning the second opening 409, such as shown in
In some embodiments, such as shown in
Activity 503 of the method 500 includes bonding the patterned surface of the second substrate 407 to an exposed surface of the multilayer stack, here a first surface, such as described in activity 303 of the method 300 set forth in
At activity 504, the method 500 includes removing the first substrate 401 from the multilayer stack to expose a second surface of the multilayer stack. Here, the second surface of the multilayer stack is opposite of the first surface and is disposed proximate to the first substrate 401 before the first substrate 401 is removed therefrom. Removing the first substrate 401 from the multilayer stack may include any one or combination of grinding, lapping, chemical mechanical planarization (CMP), etching, or cleaving methods described in activity 304 of the method 300 set forth in
At activity 505, the method 500 includes patterning a surface of a third substrate, such as the third substrate 607 shown in
At activity 506, the method 500 includes bonding the patterned surface of the third substrate 607 to the second surface of the multilayer stack using a suitable direct bonding method. A suitable direct bonding method is described at activity 303 of the method 300 set forth in
At activity 507, the method 500 includes thinning the second and third substrates 407, 607 to thickness T(8) where the second and third openings 409, 609 are respectively disposed therethrough. Typically, thinning the second and third substrates 407, 607 includes any one or combination of grinding, lapping, CMP, or etching methods to achieve the desired thickness T(8), shown in
At activity 508, the method 500 includes removing at least portions of the first and second material layers 402, 405 to expose opposite surfaces of the membrane layer 403, such as shown in
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims
1. A flow cell device, comprising:
- a glass substrate; and
- a membrane layer disposed on the glass substrate, the membrane layer having a nanopore disposed therethrough, and the nanopore is located in a portion of the membrane layer which spans an opening formed through the glass substrate.
2. The flow cell device of claim 1, wherein the glass substrate is formed of fused silica, borosilicate, or a combination thereof.
3. The flow cell device of claim 2, wherein the nanopore has a diameter of about 100 nm or less.
4. The flow cell device of claim 3, wherein a thickness of the membrane layer is less than about 100 nm.
5. The flow cell device of claim 1, wherein the membrane layer is interposed between a first dielectric layer and a second dielectric layer to form a multilayer stack.
6. The flow cell device of claim 5, wherein
- the first and second dielectric layers are formed of silicon oxide, and
- the membrane layer is formed of silicon nitride or silicon oxynitride.
7. The flow cell device of claim 5, wherein respective openings formed through each of the first and second dielectric layers expose opposite surfaces of the membrane layer.
8. The flow cell device of claim 5, wherein the second dielectric layer is disposed on the glass substrate, the membrane layer is in contact with the second dielectric layer, and the first dielectric layer is in contact with the membrane layer.
9. The flow cell device of claim 8, wherein the glass substrate is a first substrate and the flow cell device further comprises a second substrate disposed on and in contact with the first dielectric layer, wherein an opening formed through the second substrate is aligned with the opening formed through the first dielectric layer, and the second substrate is formed of fused silica, borosilicate, or a combination thereof.
10. A nanopore sensor for biopolymer strand sequencing, comprising:
- a flow cell interposed between a first reservoir and a second reservoir, the flow cell comprising a glass substrate and a membrane layer disposed on the glass substrate, the membrane layer having a nanopore formed therethrough, and the nanopore is located in a portion of the membrane layer which spans an opening formed through the glass substrate.
11. The nanopore sensor of claim 10, wherein the glass substrate is formed of fused silica, borosilicate, or a combination thereof.
12. The nanopore sensor of claim 10, wherein the nanopore has a diameter of about 100 nm or less.
13. The nanopore sensor of claim 10, wherein the first and second reservoirs each contain an electrically conductive fluid and a respective electrode that is in communication with a voltage source.
14. The nanopore sensor of claim 13, wherein the voltage source is configured to produce an ionic current flow through the nanopore.
15. The nanopore sensor of claim 14, wherein the membrane layer is interposed between a first dielectric layer and a second dielectric layer to form a multilayer stack.
16. The nanopore sensor of claim 15, wherein the second dielectric layer is disposed on the glass substrate, the membrane layer is disposed on and in contact with the second dielectric layer, and the first dielectric layer is disposed on and in contact with the membrane layer.
17. A method of sequencing a biopolymer strand using a nanopore sensor, comprising:
- generating a current between a first reservoir and a second reservoir to draw the biopolymer strand through a nanopore of a flow cell interposed between the first reservoir and the second reservoir, wherein the flow cell comprises a membrane layer disposed on a glass substrate, the nanopore is formed through a portion of the membrane layer that spans an opening formed through the glass substrate, and the biopolymer strand comprises a plurality of monomer units that sequentially occlude the nanopore as the biopolymer strand is drawn therethrough; and
- determining, based on changes in the current as the biopolymer strand is drawn through the nanopore, a monomer unit sequence of the biopolymer strand, wherein changes in the current correspond to differences in one or more characteristics of each of the monomer units sequentially occluding the nanopore.
18. The method of claim 17, wherein the glass substrate is formed of fused silica, borosilicate, or a combination thereof.
19. The method of claim 17, wherein
- each of the first and second reservoirs contain an electrically conductive fluid and an electrode,
- each of the electrodes is electrically coupled to a voltage source, and
- a voltage from the voltage source is used to generate the current.
20. The method of claim 17, wherein
- the membrane layer is interposed between a first dielectric layer and a second dielectric layer to form a multilayer stack, and
- respective openings formed through each of the first and second dielectric layers expose opposite surfaces of the membrane layer.
Type: Application
Filed: Feb 2, 2022
Publication Date: May 19, 2022
Inventors: Joseph R. JOHNSON (Redwood City, CA), Roger QUON (Rhinebeck, NY)
Application Number: 17/591,407