SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME
A semiconductor structure and a method for forming the same are provided. The semiconductor structure includes a substrate, a gate structure over a first surface of the substrate, and a source region and a drain region in the substrate adjacent to the gate structure. The semiconductor structure further includes a channel region interposing the source and drain regions and underlying the gate structure. The semiconductor structure further includes a first layer over a second surface opposite to a first surface of the substrate, and a second layer over the first layer. The semiconductor structure further includes a sensing film over the channel region. The first opening and the second opening form a contiguous opening.
This application is a division of U.S. application Ser. No. 14/878,999, filed on Oct. 8, 2015, and claims priority thereto.
FIELDThe present disclosure relates generally to a semiconductor structure and more particularly to a semiconductor structure of a biosensor.
BACKGROUNDBiosensors are devices for sensing and detecting biomolecules and operate on the basis of electronic, electrochemical, optical, and mechanical detection principles. Biosensors that include transistors are sensors that electrically sense charges, photons, and mechanical properties of bio-entities or biomolecules. The detection can be performed by detecting the bio-entities or biomolecules themselves, or through interaction and reaction between specified reactants and bio-entities/biomolecules. Such biosensors can be manufactured using semiconductor processes, can quickly convert electric signals, and can be easily applied to integrated circuits (ICs) and MEMS.
BioFETs (biologically sensitive field-effect transistors, or bio-organic field-effect transistors) are a type of biosensor that includes a transistor for electrically sensing biomolecules or bio-entities. While BioFETs are advantageous in many respects, challenges in their fabrication and/or operation arise, for example, due to compatibility issues between the semiconductor fabrication processes, the biological applications, restrictions and/or limits on the semiconductor fabrication processes, integration of the electrical signals and biological applications, and/or other challenges arising from implementing a large scale integration (LSI) process.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
In a BioFET, the gate of a metal-oxide-semiconductor field-effect transistor (MOSFET), which controls the conductance of the semiconductor between the BioFET's source and drain contacts, is replaced by a bio- or biochemical-compatible layer or a biofunctionalized layer of immobilized probe molecules that act as surface receptors. Essentially, a BioFET is a field-effect biosensor with a semiconductor transducer. A decided advantage of BioFETs is the prospect of label-free operation. Specifically, BioFETs can avoid costly and time-consuming labeling operations such as the labeling of an analyte with, for instance, fluorescent or radioactive probes.
A typical detection mechanism for BioFETs is the conductance modulation of the transducer due to the binding of a target biomolecule or bio-entity to a sensing surface or a receptor molecule immobilized on the sensing surface of the BioFET. When the target biomolecule or bio-entity is bonded to the sensing surface or the immobilized receptor, the drain current of the BioFET is varied by the potential from the sensing surface. This change in the drain current can be measured and the bonding of the receptor and the target biomolecule or bio-entity can be identified. A great variety of biomolecules and bio-entities may be used to functionalize the sensing surface of the BioFET such as ions, enzymes, antibodies, ligands, receptors, peptides, oligonucleotides, cells of organs, organisms and pieces of organic tissue. For instance, to detect ssDNA (single-stranded deoxyribonucleic acid), the sensing surface of the BioFET may be functionalized with immobilized complementary ssDNA strands. Also, to detect various proteins such as tumor markers, the sensing surface of the BioFET may be functionalized with monoclonal antibodies.
A well is formed in a semiconductor structure of a BioFET. The well is used for receiving the target biomolecule or bio-entity. Because forming the well may comprise oxide thinning processes, dry etching processes and wet etching processes, dimensions of the well are difficult to control. Because of the variations in the processes of manufacturing a BioFET, the sensing surface is non-uniform and the sensing signals are unstable.
A method 100 of fabricating a BioFET is illustrated in
In some embodiments, the gate electrode 202 includes polysilicon. Other exemplary gate electrodes include metal gate electrodes including metal such as, Cu, W, Ti, Ta, Cr, Pt, Ag, Au; suitable metallic compounds like TiN, TaN, NiSi, CoSi; combinations thereof; and/or other suitable conductive materials. In some embodiments, the gate dielectric 204 is composed of silicon oxide. Other exemplary gate dielectrics include silicon nitride, silicon oxynitride, a dielectric with a high dielectric constant (high k) ranging from about 5 to about 100, and/or combinations thereof. Examples of high k materials include hafnium silicate, hafnium oxide, zirconium oxide, aluminum oxide, tantalum pentoxide, hafnium dioxide-alumina (HfO2—Al2O3) alloy, or combinations thereof. The FET 209 may be formed using typical CMOS processes such as, photolithography; ion implantation; diffusion; deposition including physical vapor deposition (PVD), metal evaporation or sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD), low-pressure CVD (LPCVD), high density plasma CVD (HDPCVD), atomic layer CVD (ALCVD), or spin on coating; etching including wet etching, dry etching, and plasma etching; and/or other suitable CMOS processes.
In some embodiments, the first layer 210 and the second layer 212 are adjacent and differ in etch rate to a predetermined etchant. As illustrated in
In some embodiments, the first layer 210 and the second layer 212 may be one of a nitride layer and an oxide layer. In some embodiments, the first layer 210 and the second layer 212 are made of different materials. In some embodiments, the first layer 210 is a nitride layer. In some embodiments, the first layer 210 is a silicon nitride layer. In some embodiments, the second layer 212 is an oxide layer. In some embodiments, the second layer 212 is a silicon oxide layer. The oxide layer and nitride layer have high etching selectivities of oxide to nitride. The oxide layer and nitride layer can also be etch stop layers for each other. In some embodiments, the thickness of the second layer 212 is greater than that of the first layer 210. For example, the thickness of the first layer 210 is 1000 angstrom and that of the second layer 212 is 8000 angstrom. In some embodiments, a portion of the second layer 212 is removed by etching. An etchant for etching the second layer 212 stops etching on the first layer 210. The etchant may have a selectivity of oxide to nitride greater than 10. In some embodiments, a portion of the first layer 210 is removed by using materials such as H3PO4. The material removes a portion of the first layer 210 and stops on the second surface 211 of the substrate 201. In some embodiments, the removed portions of the first layer 210 and that of the second layer 212 may be different.
In some embodiments, the sensing film 214 is made of a high-k material. In some embodiments, the sensing film 214 is selected from the group comprising Si3N4, Al2O3, TiO2, HfO2, Ta2O5, SnO2 and combinations thereof. In some embodiments, the thickness of the sensing film 214 is about 30 angstrom to about 100 angstrom. As a further example, exemplary sensing film 214 include HfO2, Ta2O5, Pt, Au, W, Ti, Al, Cu, oxides of such metals, SiO2, Si3N4, Al2O3, TiO2, TiN, ZrO2, SnO, SnO2; and/or other suitable materials. The sensing film 214 may be formed using CMOS processes such as, for example, physical vapor deposition (PVD) (sputtering), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD), low-pressure CVD (LPCVD), high density plasma CVD (HDPCVD), or atomic layer CVD (ALCVD). In some embodiments, the sensing film 214 may include a plurality of layers.
In some embodiments, the sensing film 214 is considered as a conformal layer capping on the stacked structure over the second surface 211. As in
Referring back to
In some embodiments, the third layer 216 is one of a nitride layer and an oxide layer. In some embodiments, the material of the third layer 216 is the same as that of the first layer 210. In some embodiments, the thickness of the third layer 216 is greater than that of the first layer 210 and the second layer 212. For example, the thickness of the third layer 216 is 8000 angstrom, the thickness of the first layer 210 is 1000 angstrom and the thickness of the second layer 212 is also 1000 angstrom. The first, second, and third layers can each be an etch stop layer for one another. In some embodiments, a portion of the third layer 216 is removed by etching. A first etchant for etching the third layer 216 stops etching on the second layer 212. The first etchant may have a selectivity of oxide to nitride greater than 10. In some embodiments, a portion of the second layer 21 is removed by etching. A second etchant for etching the second layer 212 stops etching on the first layer 210. The second etchant may have a selectivity of oxide to nitride different from the first etchant. In some embodiments, the second etchant may have a lesser selectivity of oxide to nitride than the first etchant. For example, the second etchant may have a selectivity of oxide to nitride greater than 5. In some embodiments, a portion of the first layer 210 is removed using a material such as a buffer oxide etch (BOE). The material removes the portion of the first layer 210 and stops on the second surface 211 of the substrate 201. In some embodiments, the removed portions of the first layer 210, the second layer 212 and the third layer 216 may be different. In some embodiments, the width of the removed portion of the third layer 216 and that of the first layer 210 are greater than that of the second layer 212. The semiconductor structure of
In some embodiments, the first layer 210, the second layer 212 and the third layer 216 are adjacent and differ in etch rate to a predetermined etchant. As illustrated in
In some embodiments, the sensing film 214 is considered as a conformal layer capping on the stacked structure and over the second surface 211. As in
In some embodiments, the substrate 201 in
The same reference numerals in different drawings refer to the same element.
In some embodiments, the sensing film 214 may be formed prior to forming the first layer 210. In
As in
Referring to
The carrier substrate 602 is attached to the substrate by bonding. In some embodiments, the carrier substrate 602 is bonded to the last MLI layer. In an embodiment, the carrier substrate is bonded to a passivation layer formed on the MLI and/or ILD layers of the substrate. The carrier substrate 602 may be attached to the substrate 201 using fusion, diffusion, eutectic bonding, and/or other suitable bonding methods. Exemplary compositions for the carrier substrate 602 include silicon, glass, and quartz. In some embodiments, the carrier substrate 602 may include other functionalities such as; interconnect features, bonding sites, defined cavities, and/or other suitable features.
Referring to
Referring to
In some embodiments, a semiconductor structure comprises a substrate, a gate structure over a first surface of the substrate, and a source region and a drain region in the substrate adjacent to the gate structure. The semiconductor structure further comprises a channel region interposing the source and drain regions and underlying the gate structure. The semiconductor structure further comprises a first layer over a second surface of the substrate opposite to the first surface, and a second layer over the first layer. The semiconductor structure further comprises a sensing film over the channel region and at least a portion of the first and second layers, and a well over the sensing film and cutting off the first layer and the second layer.
In some embodiments, the first layer is one of a nitride layer and an oxide layer. In some embodiments, the second layer is one of a nitride layer and an oxide layer. In some embodiments, the first and second layers are of different materials. In some embodiments, the semiconductor structure further comprises a third layer over the second layer. In some embodiments, the third layer is one of a nitride layer and an oxide layer. In some embodiments, the material of the third layer is the same as that of the first layer. In some embodiments, the thickness of the third layer is different from that of the first layer. In some embodiments, the sensing film comprises a material with a dielectric constant ranging from 5 to 100. In some embodiments, the substrate is a silicon-on-insulator (SOI) substrate.
In some embodiments, a semiconductor structure comprises a FET device on a substrate, wherein the FET device includes a gate structure formed over a first surface of the substrate and a channel region in the substrate below the gate structure. In some embodiments, the first surface of the substrate is attached to a carrier substrate and the channel region is away from a second surface of the substrate. In some embodiments, a sensing film is formed over the channel region on the second surface of the substrate opposite to the first surface. In some embodiments, a first layer is formed over the sensing film and a second layer is formed over the first layer. In some embodiments, a well is formed over the sensing film and cutting off the first layer and the second layer.
In some embodiments, the semiconductor structure further comprises a third layer over the second layer. In some embodiments, relative to the first layer, the second layer has a protrusion extended inwardly toward the center of the well. In some embodiments, the well is defined by the openings in the first, second and third layers. In some embodiments, the lateral widths of the first, second and third layer are different. In some embodiments, the lateral width of the first layer is greater than the widths of the second and third layers.
In some embodiments, a method for forming a semiconductor structure comprises forming a substrate, forming a gate structure over a first surface of the substrate, and forming a source region and a drain region in the substrate adjacent to the gate structure. The method further comprises forming a channel region interposing the source and drain regions and underlying the gate structure. The method further comprises forming a first layer over a second surface of the substrate opposite to the first surface and forming a second layer over the first layer. The method further comprises forming a sensing film over the channel region and over at least a portion of the first and second layers, and forming a well over the sensing film and cutting off the first layer and the second layer.
In some embodiments, the method further comprises forming a third layer over the second layer. In some embodiments, the etching selectivity of the second layer and that of the third layer are different. In some embodiments, forming the well over the channel region and cutting off the first layer and the second layer further comprises removing a portion of the first layer and the second layer by etching.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
Claims
1. A method for forming a semiconductor structure, comprising:
- receiving a substrate;
- forming a gate structure over a first surface of the substrate;
- forming a source region and a drain region in the substrate adjacent to the gate structure;
- forming a channel region interposing the source and drain regions and underlying the gate structure;
- forming a sensing film over a second surface of the substrate opposite to the first surface;
- forming a first layer over the sensing film;
- forming a second layer over the first layer; and
- forming a contiguous opening in the first layer and the second layer thereby exposing a portion of the sensing film over the channel region.
2. The method of claim 1, wherein the contiguous opening is formed by removing a portion of the second layer and a portion of the first layer to form a first opening in the first layer and a second opening in the second layer, and a first width of the first opening is greater than a second width of the second opening.
3. The method of claim 2, wherein the first opening and the second opening are formed by etching, and an etching selectivity of the second layer and that of the first layer are different.
4. The method of claim 3, wherein the etching in the formation of the second opening stops on the first layer.
5. The method of claim 1, prior to formation of the contiguous opening, further comprising:
- forming a third layer over the second layer;
- wherein the contiguous opening is formed in the first layer, the second layer and the third layer thereby exposing the portion of the sensing film over the channel region.
6. The method of claim 5, wherein an etching selectivity of the second layer and that of the third layer are different.
7. The method of claim 5, wherein a first opening is formed in the first layer, a second opening is formed in the second layer, a third opening is formed in the third layer, a first width of the first opening is greater than a second width of the second opening, and a third width of the third opening is greater than the second width of the second opening.
8. The method of claim 1, wherein the sensing film is formed over the source region, the drain region, and the channel region in their entirety.
9. A semiconductor structure, comprising:
- a FET device on a substrate, wherein the FET device includes: a gate structure over a first surface of the substrate; and a channel region in the substrate below the gate structure;
- a sensing film over the second surface;
- a first layer over the sensing film and separated from the substrate by the sensing film, the first layer having a first opening of a first width over the channel region; and
- a second layer over the first layer, the second layer having a second opening of a second width over the channel region;
- wherein the first opening and the second opening form a contiguous opening, and the first width of the first opening is greater than the second width of the second opening.
10. The semiconductor structure of claim 9, further comprising:
- a third layer over the second layer, the third layer having a third opening of a third width over the channel region, wherein the first opening, the second opening, and the third opening form a contiguous opening over the sensing film.
11. The semiconductor structure of claim 10, wherein the third width of the third opening is greater than the second width of the second opening.
12. The semiconductor structure of claim 10, wherein the sensing film is over the source region, the drain region, and the channel region in their entirety.
13. The semiconductor structure of claim 9, wherein a thickness of the first layer is thinner than a thickness of the second layer.
14. A method for forming a semiconductor structure, comprising:
- receiving a silicon-on-insulator (SOI) substrate including a semiconductor layer and a buried oxide (BOX) layer over the semiconductor layer;
- forming a gate structure over a first surface of the semiconductor layer away from the BOX layer;
- forming a source region and a drain region in the substrate adjacent to the gate structure;
- forming a channel region interposing the source and drain regions and underlying the gate structure;
- removing a portion of the BOX layer to form a first layer over a second surface of the substrate opposite to the first surface;
- forming a second layer over the first layer;
- forming a third layer over the second layer;
- forming a contiguous opening in the first layer, the second layer and the third layer; and
- forming a sensing film in the contiguous opening.
15. The method of claim 14, wherein a portion of the contiguous opening in the first layer and a portion of the contiguous opening in the second layer are formed by etching operations.
16. The method of claim 15, wherein an etching selectivity of the first layer and that of the second layer are different.
17. The method of claim 15, wherein the etching operations in the formation of the portion of the contiguous opening in the first layer stops on the second surface of the semiconductor layer.
18. The method of claim 14, wherein the first layer and the third layer are composed of same material.
19. The method of claim 14, wherein the contiguous opening comprises a first opening in the first layer, a second opening in the second layer and a third opening in the third layer, the first opening is formed after the second opening, and the second opening is formed after the third opening.
20. The method of claim 14, wherein the first layer is an etch stop layer for the second layer and the second layer is an etch stop layer for the third layer.
Type: Application
Filed: Aug 8, 2018
Publication Date: Dec 20, 2018
Inventors: SHIH-WEI LIN (TAIPEI CITY), CHANG-MING WU (NEW TAIPEI CITY), LEE-CHUAN TSENG (NEW TAIPEI CITY), SHIH-CHANG LIU (KAOHSIUNG COUNTY)
Application Number: 16/058,905