KR100716937B1 - Fabrication method for a nanowire device - Google Patents

Abstract

The present invention relates to a method for enabling nanowire device fabrication in large quantities. After fabricating a nanowire pattern having a diameter of about several hundred nm by a conventional photolithography process and a silicon dry etching process on a silicon wafer, a silicon thermal oxidation process and an oxide film are performed. The removal process is used to fabricate nanowires ranging in size from several nanometers to several tens of nanometers in diameter. Then, the present invention provides a method of fabricating a nanowire device by transferring the same to another substrate on which an insulating film is formed. By using the method of transferring the nanowires from the nanowire-fabricated wafer to another wafer having the insulating film formed therein, no nanowire alignment process for placing the nanowires at the intended location is unnecessary and there is no need to use an SOI wafer.

Silicon Nanowires, Nanowire Release, Transfer

Description

Fabrication method for a nanowire device

1A and 1B are process diagrams illustrating a method of manufacturing a bottom up nanowire device;

2a to 2d is a process diagram showing a top down nanowire device manufacturing method;

3A to 3I are flowcharts illustrating a method for manufacturing a nanowire device according to a first embodiment of the present invention;

Figures 4a to 4b is a process chart showing a nanowire device manufacturing method according to a second embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

210: silicon (Si) 220: insulating layer (SiO ₂ )

230: substrate (Si) 240: photoresist patterning (nano line width)

250, 370, 410: silicon nanowires

260, 400, and 420: metal electrodes

310: silicon substrate 320: photoresist patterning

330: undercut 340: silicon oxide film

350: oxidation 360: silicon (Si)

375: nanowire support pillar 380: adhesive

390: insulation layer

1. US Patent US5,666,190 "Method of Performing Lithography Using Cantilever Array"

2. US Patent Publication US2003 / 0022470 "A1 Parallel, Individually Addressable Probe for Nanolithography"

The present invention relates to a method for manufacturing a nanowire device, and more particularly, to a method for manufacturing a nanowire device that fabricates a silicon nanowire using a silicon substrate and then transfers the silicon nanowire onto another substrate and forms an electrode structure.

Nanowires are nanoscale structures with diameters ranging from several nanometers (nm) to several tens of nanometers (nm) and with large aspect ratios ranging from tens to hundreds of days. It can be used as a transistor which is a core part of the device, and can be used as various chemical sensors and biosensors.

The fabrication of such nanowire devices can be classified into two types according to the approach. One is to use a conventional semiconductor process, particularly an ultra-fine photolithography process, to etch a material such as silicon to directly insert a nanowire device at a desired position. There is a bottom-up that uses top-down and nanowires to be synthesized using a VLS (Vapor-Liquid Solid) growth method and then arranges them to a specific position to produce nanowire devices.

 1 shows a method of fabricating a nanowire device from the bottom up. VLS growth method is used for nanowire growth of most semiconductor and metal materials such as Si, ZnO, GaN, InP, and metal and is the most researched method in nanowire field. However, in order to fabricate the nanowire device after growing the nanowire, it is necessary to align the fabricated nanowire structure in a desired position and manufacture additional structures such as electrodes. Here, as a method for aligning the nanowire structure to a desired position, a dielectrophoresis method or a fluid flow method using a fluid channel has been reported, but commercialization has not been achieved. In addition, there is a problem in that electron beam lithography (e-beam lithography), which is mainly expensive, is used to fabricate electrodes on both ends of the aligned nanowires.

Harvard's Lieber Group, the first company to announce nanowire FET sensors, also features individual nanowires using an alignment process using nanowires fabricated using VLS growth technology and an electrode formation process using e-beam lithography. Although the device is manufactured, the yield is low.

2 is a top-down nanowire device manufacturing method of directly cutting nano silicon to fabricate nanowires. In order to form nanowires having a diameter of several nanometers (nm) to several tens of nanometers (nm), it is necessary to manufacture an ultrafine pattern, and thus, an ultrafine patterning process such as electron beam lithography is used. Top-down nanowires have the advantage of being able to manufacture nanowires in desired sizes at desired locations.However, production speeds must be increased because expensive equipment such as electron beam lithography must be used. Is very slow, so there is a problem in commercialization. In addition, since the nanowires need to be fabricated on an insulator in order to serve as an electrical device, there is a problem that a silicon on insulator (SOI) wafer is used.

An object of the present invention is to solve the above problems, to provide a method for manufacturing a low-cost nanowire device capable of mass production.

It is still another object of the present invention to provide a method for fabricating nanowire devices without the need for a separate nanowire alignment process or SOI wafer by transferring silicon nanowires separated from a substrate to another oxide or insulating film wafer.

Still another object of the present invention is to provide a nanowire device manufacturing method capable of manufacturing various types of nanowires without being constrained to the crystallographic direction of a silicon substrate during the production of nanowires.

It is yet another object of the present invention to provide a method for fabricating nanowire devices without the need for a SOI wafer or a separate substrate for transfer.

The object of the present invention is to pattern a silicon first substrate, to form a vertical pillar structure having a support pillar structure and an undercut shape on the silicon substrate by a dry etching process, a silicon nanowire by a thermal oxidation process Forming silicon oxide, releasing the silicon nanowires from the first substrate by an oxide film etching process, transferring the silicon nanowires of the first substrate to a second substrate, and forming an electrode on the second substrate. It is achieved by a silicon nanowire device manufacturing method comprising.

The object of the present invention is to pattern a silicon substrate, to form a vertical trench structure having an undercut shape at the bottom by a dry etching process, to form a thermal oxide film to form a silicon nanowire, silicon nanowires of The oxide layer between the nanowires and the substrate is exposed while the upper layer is exposed, thereby achieving the silicon nanowire device manufacturing method including etching the oxide layer and forming an electrode on the substrate.

The nanowire device manufacturing method according to the present invention is to manufacture a nanowire device by manufacturing a nanowire at the wafer level using a silicon substrate and then transferring the nanowire on another substrate and patterning a metal electrode by photolithography. Since the nanowires are manufactured by etching silicon, no separate nanowire alignment is required, and since the nanowires are transferred from the substrate on which the nanowires are manufactured by the wafer contact method to the oxide or insulating film substrate, there is no need to use an SOI wafer. Transfer of nanowires to other substrates can be made with the help of polymers such as photoresist or adhesives that have good adhesion properties to the wafer substrate to be transferred, and the nanowires are directly attached to the substrates through a bonding process. It can also be fixed. After the transfer of the pattern of the nanowires by the transfer, the adhesive is removed by dry etching using oxygen plasma, and even after the adhesive is removed, the nanowire remains on the surface of the substrate by adhesion. The fabrication of an electrode structure for electrical contact on the substrate to which the nanowires are transferred is possible in the subsequent process to produce nanowire devices at the wafer level, thereby enabling the production of nanowire devices at low cost.

In addition, the present invention provides a method for manufacturing a nanowire device using a substrate on which the nanowires are formed without transferring the nanowires from the substrate on which the nanowires are formed to another substrate on which the insulating film is formed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a process diagram of manufacturing a nanowire device according to an embodiment of the present invention. First, the silicon substrate 310 is prepared and then photoresist patterned 320 through a photolithography process (FIGS. 3A to 3B). In this case, when using a stepper as a photolithography process, a line width of several hundred nanometers (nm) can be realized, and when using phase shift contact lithography, a line width of about 100 to 200 nm can be realized. If line widths of several nanometers to several tens of nanometers are required, E-beam lithography can be used. After forming the photoresist pattern, a vertical trench structure is formed as shown in FIG. 3C through a silicon dry etching process such as reactive ion etching (RIE). The silicon dry etching which induced the scallop process of deep reactive ion etching (Deep RIE) to form an undercut 330 in the lower portion of the vertical trench structure in the silicon substrate 310 fabricated as shown in FIG. 3D. Perform the process. In this case, deep reactive ion etching It may be used Bache (Bosch) process. The reason for forming the undercut (330) under the trench structure as shown in Figure 3d above is to form a narrow lower end of the silicon nanowires in the oxide film forming process of Figure 3e to electrically separate the nanowires from the substrate through the thermal oxidation process To insulate. The thermal oxidation process of FIG. 3e produces silicon nanowire structures ranging in size from several nanometers to several tens of nanometers (nm). By controlling the thermal oxidation process time, the diameter of the silicon nanowires can be reduced to several nanometers to several tens of nanometers (nm). When the oxide film 340 is removed by hydrofluoric acid vapor (HF vapor) or buffered oxide etchant (BOE), nanowires having a size of several nanometers to several tens of nanometers are obtained (Fig. 3f).

When the oxide film is removed, the nanowires become a floating structure, so that during the removal of the oxide film, the support pillars are formed at both ends of the nanowires so as to prevent the nanowires from being lost or damaged (FIGS. 3A and 3B). A pattern for 375 is also formed. The support pillar 375 is wider than the width of the nanowire so that the support pillar 375 remains stable on the silicon substrate even after the thermal oxidation process and the oxide film etching. However, if the support pillar 375 is made too large, the substrate during the nanowire transfer process Increase the contact area of the board so that it may have an unnecessary effect upon separation after board contact, so adjust the area accordingly.

Meanwhile, since the silicon nanowires are manufactured by using a dry etching process, a thermal oxidation process, and an oxide film etching process, nanowires can be manufactured regardless of the crystal direction of the silicon substrate, and thus nanowires of various shapes such as straight lines or curves can be manufactured. Do.

3G to 3H illustrate a method of transferring a nanowire 370 fabricated using a silicon thermal oxidation process and an oxide layer etch to another substrate. The substrate to which the nanowires are to be transferred uses a silicon wafer on which an oxide film or a nitride film 390 is deposited in consideration of being manufactured as an electrical device. In addition, a crystal, ceramic, glass, and polymer may be used.

Uniformly spin coat an adhesive 380 on the substrate for nanowire transfer. The adhesive 380 serves to adhere the nanowires 370, and after the nanowires 370 are transferred, the adhesive 380 may be removed by performing a plasma asing process. The adhesive 380 may be a photoresist, polydimethylsiloxane (PDMS: polydimethylsilioxine), a flexible polymer, an adhesive polymer, a thermal reflow polymer. In the case of using a photoresist, nanowire transfer can be easily performed by using the characteristics of the photoresist that is reflowed when heat is applied. At the nano size, since adhesion by surface tension acts as a major force, nanowire transfer is possible by using a polymer-based adhesive such as a photoresist, and then, even if the polymer is removed, the transferred nanowire 370 is used for adhesion. As a result, the state of the nanowires 370 transferred to the oxide film substrate may not be significantly changed even after the polymer is removed.

Alternatively, according to another embodiment of the present invention, before performing the transfer process of the silicon nanowires, the pressure-sensitive adhesive for transferring the nanowires by performing a photolithography process or an imprinting process after coating the adhesive 380 to the substrate to be transferred Patterns can be formed. By transferring the nanowires on the pressure-sensitive adhesive pattern, the nanowires can be transferred only to the intended position of the substrate to be transferred, and at the same time, the number of nanowires transferred to the substrate to be transferred can be controlled. It is possible to improve the degree of integration.

Alternatively, according to another embodiment of the present invention, after forming the alignment marker pattern on the substrate to be transferred, an adhesive pattern may be formed. The alignment mark pattern facilitates the process by performing the role of the alignment marker in performing the adhesive pattern formation, nanowire transfer and electrode formation process, and the density of nanowire devices when the nanowire transfer process is repeatedly performed. Can improve.

Alternatively, according to another embodiment of the present invention, the nanowires may be transferred by directly fixing the silicon nanowires to the substrate through various bonding processes without using an adhesive. As an example, a nanowire-transferred substrate is specifically used for coating or removing an adhesive using a polydimethylsilioxine (PDMS), such as a flexible substrate or a sticky substrate, which has a self-adhesive property. The process of making it can be skipped.

When the silicon nanowire is directly fixed to the substrate without using an adhesive, according to another embodiment of the present invention, the substrate to be transferred is subjected to a hot embossing process prior to the transfer process of the nanowire to form an adhesive pattern. can do. Alternatively, according to another embodiment of the present invention, an adhesive pattern may be formed after the alignment mark pattern is formed on the substrate to be transferred.

In this case, the first silicon substrate on which the nanowires 370 are formed and the substrate to which the nanowires are to be transferred are brought into close contact with each other, and then the nanowires 370 are adhered to the substrate to be transferred by applying heat and pressure. At this time, the heat and pressure may be determined according to the material of the substrate to be transferred under the condition that the transfer efficiency of the nanowire 370 is high.

Then, when the electrode structure 400 for electrical contact is formed on the substrate to which the nanowires are transferred, the nanowire device manufacturing process is completed (FIG. 3i). When the metal thin film used as the material of the electrode 400 is deposited, the nanowires are permanently fixed to the surface of the substrate, so that the nanowires may be lost even if a wet process is added. In order to form the electrode 400 on the substrate to which the nanowires are transferred, an additional process may be performed in units of wafers, and the pattern alignment may be easily performed by aligning using the alignment pattern of the mask and the pattern of the nanowire.

Figure 4 is a nanowire device manufacturing process according to another embodiment of the present invention, this embodiment is the same process as the other embodiment to the process of forming the nanowire structure shown in Figures 3a to 3e. However, in the present embodiment, after the nanowire structure manufacturing process of FIG. 3E is completed, the oxide layer covering the upper layer of the nanowire 410 is removed by dry etching such as reactive ion etching (RIE) (Fig. 4A), and then the electrical An electrode structure 420 is formed for the contact (Fig. 4b). Thus, a nanowire device manufacturing process is possible on a silicon substrate without using a conventional SOI substrate or a separate substrate to be transferred as in other embodiments. In this case, according to another embodiment of the present invention, after the electrode 420 is formed, it is also possible to manufacture a nanowire device floating in the air by removing an oxide film under the nanowire.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The nanowire device manufacturing method according to the present invention can mass-produce a desired number of nanowires at a desired position without using an SOI wafer.

While using a conventional photolithography process on a silicon substrate, a silicon structure having a narrow trench structure at the bottom is formed and then thermally oxidized to have a size of several nanometers to several tens of nanometers isolated from the substrate. Single crystal silicon nanowires can be easily fabricated and transferred to other wafers to enable mass production of nanowire devices without the need for separate nanowire alignment processes or SOI wafers. In addition, since the nanowire manufacturing process is manufactured by using a dry etching process and a thermal oxide film forming process, a much more uniform nanowire can be obtained than a conventional manufacturing process. Regardless, it is easy to manufacture nanowires of a desired crystal structure, and nanowires can also be manufactured in various shapes such as straight lines and curves. It is also applicable to the fabrication of silicon nanowire devices having intended electrical properties by adding appropriate impurities to the silicon nanowires during the formation of the nanowires. The nanowire devices manufactured by the present invention can be applied to devices such as nanowire FETs, nanowire biosensors, flexible displays, and the like, thereby securing productivity for enabling nanowire device manufacturing and mass production.

Claims (16)

Patterning the silicon first substrate; Dry etching to form a support pillar structure on the silicon first substrate and a vertical trench structure having an undercut shape thereunder; Thermally oxidizing the silicon first substrate to form silicon nanowires; Etching the thermal oxide film formed on the silicon first substrate such that the silicon nanowires are released from the silicon first substrate; Transferring silicon nanowires of the silicon first substrate to a second substrate; And Forming an electrode on the second substrate Silicon nanowire device manufacturing method comprising a. The method of claim 1, The dry etching step Reactive ion etching the silicon first substrate; And Deep reactive ion etching of the silicon first substrate Silicon nanowire device manufacturing method comprising a. The method of claim 2, Forming the silicon nanowires, And all the undercut portions of the lower portion are oxidized to separate silicon nanowires from the first substrate. The method of claim 3, wherein And uniformly coating a pressure-sensitive adhesive on the second substrate before transferring the silicon nanowires to a second substrate, And removing the adhesive from the second substrate after transferring the silicon nanowires to a second substrate. The method of claim 4, wherein Removing the pressure-sensitive adhesive from the second substrate is a silicon nanowire device manufacturing method performed by plasma dry etching. The method of claim 4, wherein Between uniformly coating the pressure-sensitive adhesive on the second substrate and transferring the silicon nanowires, The method of manufacturing a silicon nanowire device further comprising the step of forming a pattern on the coated pressure-sensitive adhesive. The method of claim 6, Forming a pattern on the coated adhesive is a nanowire device manufacturing method performed by a photolithography process or an imprinting process. The method according to any one of claims 1 to 7, The second substrate is a silicon nanowire device manufacturing method of any one of silicon, quartz, ceramic, glass and polymer (polymer). The method of claim 3, wherein The second substrate is a silicon nanowire device manufacturing method is a flexible substrate or a viscous substrate. The method of claim 9, Before transferring the nanowires The method of manufacturing the nanowire device further comprising forming a pressure-sensitive adhesive pattern by performing a hot embossing process on the second substrate. The method according to claim 4 or 9, Transferring the nanowires, Adhering the nanowires to the second substrate; And Separating the adhered nanowires from the first substrate Silicon nanowire device manufacturing method comprising a. The method of claim 11, wherein Silicon nanowire device manufacturing method of applying heat and pressure in the process of adhering the nanowires to the second substrate. The method of claim 11, wherein Before forming the pressure-sensitive adhesive pattern on the second substrate further comprises the step of forming a label pattern for alignment. Patterning the silicon substrate; Forming a vertical trench structure having an undercut shape in a lower portion by a dry etching process; Forming a thermal oxide film to form silicon nanowires; Etching the oxide layer so that the oxide layer between the nanowire and the substrate is not completely removed while the upper portion of the silicon nanowire is exposed; And Forming an electrode on the substrate Silicon nanowire device manufacturing method comprising a. The method of claim 14, The etching of the oxide layer is a method of manufacturing a silicon nanowire device using wet etching or dry etching. The method of claim 14, After forming an electrode on the substrate And etching the oxide film to release the nanowires from the silicon nanowire substrate.

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