KR20060000809A - Afm cantilever having fet structure of high aspect ratio for use in liquid and method for fabricating the same - Google Patents

Abstract

The present invention relates to an atomic force microscope cantilever having a high aspect ratio single-electron transistor structure usable in a liquid, and to a method of manufacturing the same. The present invention relates to an atomic force microscope cantilever having a field effect transistor having a microchannel of 100 nm or less. For atomic force microscopy, which can analyze biomolecules, prevent the occurrence of short channel effects caused by microchannels, and increase the aspect ratio of the probe to improve the degree of sensing of information A cantilever and a manufacturing method thereof are provided.

A method for producing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid of the present invention comprises the steps of: (a) forming a probe on top of the cantilever support; (b) After the multilayer film is formed on the cantilever support, the cantilever arm is formed such that the probe is positioned in the channel region of the field effect transistor and the source and drain regions are formed on both sides of the probe by pattern formation and impurity injection twice. Doing; (c) applying a positive photoresist of the same thickness to the top of the substrate so that only the tip of the probe is visible or a thick application of the positive photoresist to ashing to expose the tip of the probe; (d) applying a negative photoresist on the positive photoresist and then patterning a mask to remove the negative photoresist at the tip of the probe; (e) depositing a metal point only on the tip of the probe from which the negative photoresist has been removed; And (e) removing a portion of the cantilever arm to float the cantilever arm. A method of manufacturing an atomic force microscopy cantilever having a high aspect ratio single electron transistor structure usable in a liquid.

Therefore, the atomic force microscope cantilever having a high aspect ratio single-electron transistor structure usable in the liquid of the present invention and its manufacturing method have the advantage of attaching a single molecule to the probe by measuring the electrical effect of the interaction between the biomolecules. This has the effect of increasing reception sensitivity.

AFM, Cantilever, Charge Measurement, Aspect Ratio, Microscope, Transistor

Description

AFM cantilever having FET structure of high aspect ratio for use in liquid and method for fabricating the same}             

1A to 1I are partial process diagrams of a method for manufacturing cantilever for atomic force microscope according to the present invention.

2 is a plan view of FIG. 1H.

3A to 3D are cross-sectional views taken along line AA ′ of FIG. 2.

4 is a plan view of a state in which the process of Figure 3e is completed.

5 shows, in plan view, the subsequent process of FIG. 3E;

Figure 6a to 6c is a cantilever shape forming process according to the present invention.

7A to 7D are cross-sectional views for forming a metal film on an atomic force microscope cantilever according to the present invention.

8A to 8D are schematic cross-sectional views of cantilevers for atomic force microscopes with high vertical aspect ratios in accordance with the present invention;

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

110,130: silicon layer 120,141,142,151,152: insulating film

131a, 204, 300: probe 153: polysilicon layer

154,910,920,930: photoresist film 157,161: mask pattern

171: channel region 191: impurity doping region

203: channel 210: source

220: drain 820: metal point

The present invention relates to a method for manufacturing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, and more particularly, to an atomic force microscope cantilever having a field effect transistor having a microchannel of 100 nm or less. Can be used to analyze biomolecules, prevent short channel effects caused by microchannels, and increase the aspect ratio of the probe, improving the sensitivity of the information. A cantilever for a microscope and a method for producing the same.

An important sensor part when studying biomolecules using an atomic force microscope in the past is the cantilever. The cantilever is generally used by coating gold (Au) with a material such as silicon (Si), silicon oxide film (SiO ₂ ), or silicon nitride film (Si ₃ N ₄ ).

Most of the biomaterials have a very good adhesion to the surface of the gold, and in order to attach any specific group to the cantilever, a gold-coated cantilever is coated with a material that can bind with a desired molecule. The cantilever is used to analyze biomolecules using a cantilever to which several molecules are attached.

Korean Patent No. 10-0366701 discloses a probe of a scanning probe microscope having a field effect transistor channel structure and a method of manufacturing the same. This means that when the source and drain formed cantilever is vertically attached to the insulator formed sample and a voltage is applied to the source, the amount of current flowing through the drain changes according to the charge distribution on the surface of the sample. However, the measured device characteristics showed typical MOSFET device characteristics, but no actual surface charge distribution was read using them.

Korean Patent Laid-Open Publication No. 2003-0041725 discloses "a single / multi-cantilever probe for atomic force microscopy and its manufacturing method" by applying a semiconductor device fabrication process to general micromachining techniques to reduce the effective channel length between source and drain. It was possible to increase the size of the array and to configure the array type in which several cantilevers can exist in one body. However, the conventional cantilever is not coated with gold at a very localized region, and thus cannot detect interactions with a single molecule. Although such single-molecule interaction research may play a very important role in the development of new drugs, there is a problem in that accurate single-molecule interactions are not yet seen.

Korean Patent Laid-Open Publication No. 2003-0041726 discloses a high-resolution single / multi-cantilever probe for atomic force microscopy and a method of manufacturing the same, in which a sharp tip is formed to read the charge distribution on the sample surface even in a more localized region. In form. In addition, in the related art, when the cantilever is driven in the liquid state, the source and drain regions are exposed to the liquid state, and the channel becomes liquid. Therefore, in order to use such cantilever in the liquid state, it is necessary to make the channel effect only at the pointed probe. In order to know the interaction of single biomolecules or the interaction between a single biomolecule and a cell, the probe must have a high aspect ratio, and there is no cantilever that has a probe portion capable of transmitting a small current change with this high aspect ratio.

Accordingly, the present invention is to solve the above disadvantages and problems of the prior art, there is an advantage of attaching a single molecule to the probe by measuring the electrical effect of the interaction between the biomolecules, the reception sensitivity is increased It is an object of the present invention to provide a method for producing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid such that the effect is exhibited.

The object of the present invention is a cantilever support; A cantilever arm positioned on the cantilever support object and one side of which is injured; A probe located at the tip of the cantilever arm; A channel located in the cantilever arm below the probe; Source and drain, respectively located on both sides of the channel; And a high aspect ratio single electron transistor structure usable in a liquid comprising a metal point located at the tip of the probe.

Another object of the present invention is to form a probe on top of (a) the cantilever support; (b) After the multilayer film is formed on the cantilever support, the cantilever arm is formed such that the probe is positioned in the channel region of the field effect transistor and the source and drain regions are formed on both sides of the probe by pattern formation and impurity injection twice. Doing; (c) applying a positive photoresist of the same thickness to the top of the substrate so that only the tip of the probe is visible or a thick application of the positive photoresist to ashing to expose the tip of the probe; (d) applying a negative photoresist on the positive photoresist and then patterning a mask to remove the negative photoresist at the tip of the probe; (e) depositing a metal point only on the tip of the probe from which the negative photoresist has been removed; And (e) removing a portion of the cantilever arm to float the cantilever arm. A method of manufacturing an atomic force microscopy cantilever having a high aspect ratio single electron transistor structure usable in a liquid.

The cantilever proposed in the present invention is an atomic force microscopy cantilever with a field effect transistor and can attach only a single molecule to the cantilever to measure minute current changes occurring between liquid single molecules or between single molecules and cells. The better sensitivity interaction can be measured.

Details of the above object and technical configuration of the present invention and the effects thereof according to the present invention will be more clearly understood by the following detailed description with reference to the drawings showing preferred embodiments of the present invention.

1A to 1I are a partial process diagram of a method for manufacturing an atomic force microscope probe having a high vertical aspect ratio according to the present invention.

First, as shown in FIG. 1A, each of the upper and lower portions of a silicon on insulator (SOI) substrate on which the first silicon layer 110, the first insulating layer 120, and the second silicon layer 130 are sequentially stacked is disposed. The first upper insulating layer 141 and the first lower insulating layer 142 are formed. The insulating films 141 and 142 are formed to a thickness of about 1 μm through, for example, a wet oxidation process using water as a silicon oxide film.

Next, as shown in FIG. 1B, a photoresist film 150 is formed on the first upper insulating film 141, and a pattern for forming a probe through photolithography and dry etching is formed.

Next, as illustrated in FIG. 1C, after the pattern for forming the probe is formed, the photoresist layer formed on the first upper insulating layer 141 is removed. In the method of removing the photoresist film, it is preferable to heat H ₂ SO ₄ and H ₂ O ₂ at a ratio of 4: 1 at 120 ° C. for 10 minutes or more, and in addition to the above method, when the photoresist film is not removed, The photosensitive film may be burned off by an O ₂ plasma (Oxygen Plasma) method.

FIG. 1D is a dry etching of the second silicon layer 130 using SF ₆ gas. When the second silicon layer 130 is stacked to a thickness of 4.0 ± 0.5 micrometers (μm), it is preferable to form a probe having a height of 3.6 ± 0.5 micrometers.

In FIG. 1E, the upper first upper insulating layer 141 and the lower first lower insulating layer 142 obtained through the photolithography process are etched. Etching is performed using a wet etching method using a mixture of BHF (Buffered HF) and H ₂ O in a volume ratio of 7: 1. At this time, a probe shape is formed and a cone shape is formed.

The probe shape may be formed in a cone shape and a pyramidal type. The length and size of the cone and pyramid shape vary with the degree of etching, but there is no difference between the two types. The cone shape is formed using a plasma etching method, and the pyramid shape is formed using wet etching. The plasma etching method for forming the cone shape is used in the present invention because of the advantage of uniformly appearing throughout the wafer.

1F and 1G form the second upper insulating layer 131 and the second lower insulating layer 132 to remove the second silicon layer 130 around the probe. Third insulating layers 131 and 132 are formed on the second silicon layer 130 by a wet thermal oxidation method. The second silicon layer 130 around the probe is wet-etched by including the formed second upper insulating layer 131 and the second lower insulating layer 132. Wet etching uses a solution in which BHF and H ₂ O are mixed at a volume ratio of 7: 1. Since the density of the first insulating layer 120 constituting the SOI is higher than that of the second upper insulating layer 131, the first insulating layer is hardly etched during etching. This process may be repeated one or more times until the second silicon layer 130 around the probe is completely removed.

Figure 1g (a) is a shape when the probe is in the form of a cone, Figure 1g (b) is a shape when the probe is in the form of a pyramid. In the process of FIG. 1E, there is no significant difference depending on whether plasma etching or wet etching is used.

In FIG. 1H, a second insulating film 151, a third insulating film 152, a polysilicon layer 153, and a photoresist film 154 are sequentially stacked on the probe and the first insulating film 120, and photoetched. The first mask pattern 157 having a pattern for forming a source and a drain is formed on the polysilicon layer 153 by performing the process. The second insulating film 151 and the third insulating film 152 may be formed of a heterogeneous material, and each of the second insulating film 151 and the third insulating film 152 may be formed of one selected from a silicon nitride film and a tetraethoxysilane (TEOS) oxide film. In an embodiment of the present invention, the second insulating film 151 is formed of a silicon nitride film having a low stress, and the third insulating film 152 is formed of a TEOS oxide film.

FIG. 1I is a mask of a first mask pattern of a nuclear microscope cantilever formed of the photoresist film, and then etched from the polysilicon layer 153 to the second insulating film 151 to form a nuclear power on the first insulating film 120. The cantilever mask pattern 161 of the microscope cantilever is formed. After the etching process is completed, the photoresist film is removed by an oxygen plasma method. The cantilever mask pattern 161 is used as a mask for injecting impurities to form a source and a drain of the cantilever for an atomic force microscope having a field effect transistor.

FIG. 2 is a plan view of FIG. 1G, wherein a cantilever arm mask pattern 161 for atomic force microscopy is formed on the second silicon layer 130, and the exposed second silicon layer is an impurity doped region 191. Exist).

3A to 3E are cross-sectional views taken along the line A-A 'of FIG. 2, showing a partial process diagram for forming the microchannels of the transistors after FIG. 1G, and FIG. 3A is a cross-sectional view of FIG. The cross section of the is shown.

First, as shown in FIG. 3B, a portion of the side surface of the third insulating layer 152 made of the TEOS oxide layer is removed by wet etching. In this case, the wet etching solution uses diluted HF solution.

Next, as shown in FIG. 3C, the polysilicon layer 153 is removed.

Next, as shown in FIG. 3D, a portion of the side surface of the second insulating layer 151 made of the low stress nitride layer is removed by wet etching. Here, H ₃ PO ₄ solution is used as an etching solution to selectively wet etch only the low stress nitride film.

Next, when the third insulating layer 152 is removed, only the second insulating layer to be used as a channel mask pattern for forming a channel on the second silicon layer 130 remains as shown in FIG. 3E.

FIG. 4 is a plan view of the state in which the process of FIG. 3E is completed, and the dotted line M is the outline of the cantilever arm mask pattern 161 for atomic force microscope formed on the second silicon layer in the description of FIG. 1F described above, and the solid line m 3B illustrates the outline of the second insulating film to be used as a mask pattern for forming a channel when the process is performed from FIGS. 3B to 3E. That is, as shown in FIG. 4, the width d of the channel mask pattern becomes relatively much smaller than the width d1 of the cantilever arm mask pattern in the region where the channel is formed.

As described above, in the present invention, when forming the channel region, at least two or more insulating films made of mutually different materials are stacked on the second silicon layer of the SOI substrate, and a polysilicon layer is formed on the stacked insulating films. Thereafter, side etching of the insulating layers is sequentially performed except for the polysilicon layer, and then the width of the insulating layer on the second remaining silicon layer is reduced. Therefore, when impurities are implanted by masking the insulating film, a microchannel of 100 nm or less can be formed between the source and the drain.

FIG. 5 is a plan view of the subsequent process of FIG. 3E, and after the process of FIG. 3E, impurities are implanted. Here, the implantation of the impurity is performed by performing an ion implantation process at 70 keV energy so that the impurity concentration is approximately 1 × 10 ¹⁶ cm ⁻² , and implanting the impurity and performing heat treatment.

In this case, since the second insulating film is formed in the channel region 171, impurities may not be injected into the lower portion of the second insulating film to form the channel region. Impurities are implanted only in the exposed second silicon layer 130, and the impurity doped region 191 of FIG. 2 becomes n + or p +. A region between the dotted line 'M' of the cantilever arm mask pattern 161 for atomic force microscopes and the solid line 'm', which is the outline of the second insulating film to be used as a mask for forming a channel when the process is performed up to FIG. 3E. 192 becomes n ++ or p ++.

In this case, if the P-type impurity is doped into the second silicon layer of the aforementioned SOI substrate, the N-type impurity is implanted, and if the N-type impurity is doped into the second silicon layer, the P-type impurity is implanted.

6A to 6C are cantilever shape forming process diagrams according to the present invention. As shown in FIG. 6A, dry thermal oxidation is performed to form a thermal oxide film (SiO ₂ ) 710 on the second silicon layer 130. At this time, the thickness of the thermal oxide film 710 should be greater than or equal to 100 nm, preferably 100-110 nm. The portion where the silicon nitride film 750 is located does not form an oxide film because the probe is sharp when the oxide film is formed. After the thermal oxide film 710 is formed, the silicon nitride film 750 is removed. The silicon nitride film 750 is removed by immersion in, for example, a H ₃ PO ₄ solution at 160 ° C.

Thereafter, as shown in FIG. 6B, the second insulating film 151 is removed, a photoresist is formed on the second silicon layer, and a cantilever pattern made of photoresist is formed by a photolithography process. The cantilever arm of the second silicon layer is formed by removing the second silicon layer using the formed cantilever pattern as a mask. Here, the cantilever arm must include the source 210, drain 220, channel 203 and probe 204 described above.

FIG. 6C is an enlarged view of 'K' of FIG. 5B, in which a probe 204 is formed at the tip of the cantilever, and a channel 203 is formed below the probe 204, and the channel 203 is formed. As a reference, the source 210 and the drain 220 are formed at the left and right portions.

Each of the source 210 and the drain 220 is provided with regions 212 and 222 doped with n ++ or p ++ impurities, respectively, in contact with the channel 203, and regions 212 and 222 doped with n ++ or p ++ impurities, respectively. Adjacent to each of the regions are regions 211 and 221 doped with n + or p + impurities.

7A to 7D are cross-sectional views for forming a metal point according to the present invention. As shown in FIG. 7A, after the positive photoresist films 910 and 920 are sequentially coated on the second silicon layer 130 on which the thermal oxide film 710 is formed, the photoresist is sequentially applied. A portion of the membrane 920 is removed to make the probe visible. Alternatively, as shown in FIG. 7A (b), after the thick photoresist film 910 is applied at a time, PE-type oxygen plasma ashing is performed to make the probe part visible.

Next, as shown in FIG. 7B, after applying the negative photoresist film 930, a photolithography process is performed so that the probe part is visible.

7C is an enlarged view of the probe portion of FIG. 7B after the metal film is formed on the negative photoresist film. The metal film is preferably gold (Au), for example, and is formed through sputtering, vacuum deposition, a sol-gel process, or the like.

Next, as shown in FIG. 7D, the negative photoresist film is lifted off to form the metal point 820 by leaving the metal film only at the tip of the probe.

8A to 8D are cross-sectional views of the cantilever shape forming process according to the present invention. FIG. 8A illustrates the AZ 4620 photoresist film 900 stacked on the SOI substrate from which the second silicon layer including the metal line and the probe is removed. The photoresist film 900 serves as a protective film to sufficiently protect the device formed thereon when the first silicon layer 110 is etched. The photoresist film 900 may be used at 110 ° C. for 20 minutes and at 130 ° C. for 10 minutes. Heat treatment for minutes.

8b is a dry etching of the first silicon layer 110. If the first silicon layer 110 is wet etched, a photoresist film must be formed to sufficiently endure the solution used for the wet etch, but there is a problem in removing the film later. In addition, the wet etching method uses a dry etching method because the cantilever arm that is weakly attached to the body may be easily broken when the cantilever chip is handled. 8C is a side view of the state after the process of FIG. 8B is completed.

8D illustrates etching the first insulating film and removing the photoresist film after the process of FIG. 8B is completed. The first insulating layer 120 is wet etched using a solution in which the ultrapure water BHF solution is diluted 7: 1, and then burned off the photoresist film 900 using an oxygen plasma method.

Although the present invention has been shown and described with reference to the preferred embodiments as described above, it is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

Therefore, the method for manufacturing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in the liquid of the present invention has the advantage of attaching a single molecule to the probe by measuring the electrical effect of the interaction between the biomolecules, and receiving Sensitivity is increased.

Claims (15)

Cantilever support; A cantilever arm positioned on the cantilever support object and one side of which is injured; A probe located at the tip of the cantilever arm; A channel located in the cantilever arm below the probe; Source and drain, respectively located on both sides of the channel; And A metal point located at the tip of the probe An atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that it is configured to include. The method of claim 1, And said cantilever support comprises a first silicon layer and a first insulating film over said first silicon layer. An atomic force microscope cantilever having a high aspect ratio single electron transistor structure for use in liquids. The method of claim 1, The cantilever arm is composed of first and second arms extending in parallel with a constant width at regular intervals from each other, and the first and second arms are connected in a V shape at their distal ends. Atomic force microscopy cantilevers with possible high aspect ratio single electron transistor structures. The method of claim 1, And the probe has a cone or pyramid shape. An atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid. The method of claim 1, The probe is Silicon located above the tip of the cantilever arm; A thermal oxide film on the silicon except the peak portion; And Metal points located at the top of the attachment An atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that it is configured to include. The method of claim 1, The atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that the metal point is composed of gold. The method of claim 1, An atomic force microscopy cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that the probe has a height of 3.6 ± 0.5 micrometers. The method of claim 5, The atomic oxide microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that the thickness of the thermal oxide film formed on the second silicon layer is 100 nm to 110 nm. A method for producing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, (a) forming a probe on top of the cantilever support; (b) After the multilayer film is formed on the cantilever support, the cantilever arm is formed such that the probe is positioned in the channel region of the field effect transistor and the source and drain regions are formed on both sides of the probe by pattern formation and impurity injection twice. Doing; (c) forming a positive photoresist on the substrate to expose only the tip of the probe; (d) applying a negative photoresist on the positive photoresist and then patterning to remove the negative photoresist at the tip of the probe; (e) depositing a metal point only on the tip of the probe from which the negative photoresist has been removed; And (f) removing a portion of the cantilever arm to float the cantilever arm Method for producing an atomic force microscope cantilever having a high aspect ratio single-electron transistor structure usable in a liquid comprising a. The method of claim 9, Step (a) is Forming a mask pattern for forming a probe on the second silicon layer of the SOI substrate in which the first silicon layer, the first insulating film, and the second silicon layer are sequentially stacked; Masking the mask pattern to etch a portion of the second silicon layer to form a probe shape formed of a silicon layer; Removing the mask pattern; And Forming a thermally oxidized film on the second silicon layer and forming a pointed probe on the second silicon layer by removing the thermal oxidized film by a wet etching process. Method for producing an atomic force microscope cantilever having a high aspect ratio single-electron transistor structure usable in a liquid comprising a. The method of claim 9, Step (b) is Sequentially stacking a second insulating film, a third insulating film, a polysilicon layer, and a photoresist on the cantilever support including the probe, and etching the polysilicon layer to the second insulating film to form a cantilever arm mask pattern; Masking with the cantilever arm mask pattern to inject a first impurity into the cantilever support and heat treatment; Etching a portion of the cantilever arm mask pattern to form a channel mask pattern; Masking with the channel mask pattern to inject a second impurity and heat treatment; And Forming a cantilever arm of a second silicon layer having a shape including the probe, regions implanted with first and second impurities Method for producing an atomic force microscope cantilever having a high aspect ratio single-electron transistor structure usable in a liquid comprising a. The method of claim 9, Step (c) is a high aspect ratio single-electron transistor usable in a liquid, characterized in that the positive photoresist is applied several times so that only the tip of the probe is exposed, or the positive photoresist is thickly applied and then ashed to expose the tip of the probe. A method for producing an atomic force microscope cantilever having a structure. The method of claim 12, The ashing of step (c) is carried out using a PE type asher Atomic force microscope cantilever manufacturing method having a high aspect ratio single electron transistor structure usable in a liquid. The method of claim 9, The method of manufacturing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that the metal film of step (d) is composed of any one of gold, iron, nickel and chromium. The method of claim 9, The method of manufacturing an atomic force microscope cantilever having a high aspect ratio single electron transistor structure usable in a liquid, characterized in that the removal of the photoresist of step (d) is performed by a lift off process.

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