Method for manufacture of nanosensor

FIELD: physics.

SUBSTANCE: invention is related to micro- and nanoelectronics and may be used in production of integral silicon chemical and biosensors for automated control of environment, in ecology, in chemical production, in biology and medicine. Invention is aimed at reduction of nanosensor size, reduction of defectiveness, increased sensitivity, repeatability and efficiency, achievement of compatibility with standard industrial technology VLSI. In method for manufacture of nanosensor, which consists in the fact that dielectric layer is created on silicon substrate, and on surface of dielectric layer silicon layer is formed, from which nanowire with ohm contacts is formed via mask by etching, etching for formation of nanowire with ohm contacts of specified size is carried out in vapours of xenon difluoride with the rate of 36÷100 nm/min, at temperature of 5÷20°C, for 0.3÷1.3 min., silicon layer, from which nanowire is formed with ohm contacts by etching, is created with thickness of 11÷45 nm, and etching mask used is mask of polymer polymethyl methacrylate with thickness of 50÷150 nm.

EFFECT: reduction of nanosensor size, reduction of defectiveness, increased sensitivity, repeatability and efficiency, achievement of compatibility with standard industrial technology VLSI.

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The invention relates to micro - and nanoelectronics, nanosensors and can be used in the manufacture of integrated silicon chemical and biosensors for automated control of environment, ecology, chemical industry, biology and medicine.

A known method of manufacturing nanosensor (Z.Li, Y.Chen, X.Li, T.I.Kamins, .Nauka, R.S.Williams, "Sequence-Specific Label-Free DNA Sensors Based on Silicon Nanowires". - NANO LETTERS, Vol.4, No.2, (2004) pp.245-247), namely, that the primary sensing element of nanosensor - silicon nanowires with ohmic contacts on the dielectric layer on a silicon substrate is formed by electron lithography and reactive ion etching, which is detectionrate procedure for silicon, which is formed nanowires.

The disadvantages of the known technical solutions include the following.

First, reactive ion etching of silicon nanowires leads to defect formation in silicon (lateral amorphization of the silicon crystal in the nanowires), which reduces the sensitivity nanosensors and limits the minimum size of the working nanosensors (50 nm width nanowire).

Secondly, get the nanosensors are low sensitivity and high noise, caused, apparently, by the peculiarities of the process of reactive ionov the etching of silicon nanowires, followed in all probability the amorphization of silicon nanowires. The result of this circumstance does not allow to reduce the width of the resulting nanowires to the required values (less than 10÷30 nm).

Third, reactive ion etching of silicon nanowires structures in silicon-on-insulator has a low selectivity with respect to etching of the underlying layer, a buried silicon oxide and leads to the accumulation of movable electric charge in the buried oxide of silicon and increase leakage currents through the buried oxide.

Another known technical solution is the method of manufacturing nanosensor (Eric Stern, James F. Klemic, David A. Routenberg, Pauline N. Wyrembak, Daniel B. Turner-Evans, Andrew D. Hamilton, David A. La Van, Tarek M. Fahmy, Mark A. Reed, Label-free immunodetection with CMOS-compatible semiconducting nanowires. - Nature, Vol.445, No.7127 (2007), pp.519-522), namely, that the primary sensing element of nanosensor - silicon nanowires with ohmic contacts on the dielectric layer on the silicon substrate is formed a liquid chemical etching of silicon hydroxide of Tetramethylammonium through the mask dielectric of silicon dioxide.

The disadvantages of the known technical solutions include the following.

First, due to the nature of this method, probably due to anisotropic liquid etching kristallographie, when the face (111) etched in 100 times slower than the other facets minimum width of silicon nanowires with a trapezoidal cross-section varies from 50 nm to 100 nm (the width of the top face).

Secondly, features of liquid etching of the silicon carbon-containing organic provide the Etchant repeated attacks increased requirements to the defectiveness of the mask and the layer of silicon, and the defectiveness of the buried oxide structures in silicon-on-insulator and does not allow due to capillary effects and hydrodynamics of liquid reproducibly provide the Etchant to reduce the width of the resulting silicon nanowires to the required values (less than 10÷30 nm).

Third, the problematic use of this method in industry standard technology VLSI due to organic carbon provide the Etchant of silicon, low controllability and reproducibility of the etching liquid in the nanometer size range, low compliance with environmental and hygiene standards.

The technical result of the invention is:

- reduced size of nanosensor, respectively, increased sensitivity;

- reducing defects, improving the reproducibility and efficiency;

achieving compatibility with industry standard technology VLSI due to slow gas etching a layer of silicon on metrovoi thickness in vapor diferida xenon.

The technical result is achieved in that in the method of manufacturing nanosensor, namely, that on a silicon substrate to create a dielectric layer on the surface of which is grown a layer of silicon, from which the etching through the mask to form the nanowires with ohmic contacts, and etching to given dimensions nonprobate with ohmic contacts is carried out in vapor diferida xenon.

The silicon layer from which the etching form the nanowires with ohmic contacts, put a method DELICUT in a layer thickness of 11÷45 nm, and the etching vapor diferida xenon spend with a speed of 36÷100 nm/min at a temperature 5÷20°C within 0.3÷1,3 minutes

As the mask for etching using the mask of poly resin thickness of 50÷150 nm.

Gas chemical etching of silicon in vapor diferida xenon has a very high selectivity (>1000, <100000) with respect to the etching of the underlying dielectric layer of silicon dioxide.

For the formation of nanowires with ohmic contacts the silicon layer poison vapor diferida xenon with a speed of 36÷100 nm/min At a speed of etching is less than 36 nm/min is not the etching of the silicon layer, and forming the lower diferido silicon surface passivation layer of silicon. When etching rates greater than 100 nm/min is strong the edge roughness of the nanowires. When the temperature of the etching below 5°C in the surface layer of silicon deposited atmospheric water, which hydrolyzes SiF4, formed HF and degradation of the underlying dielectric layer of silicon dioxide. When the temperature of the etching above 20°C. the etching rate of the silicon is reduced. At the time of etching is less than 0.3 min stay neprotivlenie Islands silicon layer. At the time of etching more than 1.3 min the side of rastra silicon layer and gap nanowires. When using a mask for etching of the polymer polymethylmethacrylate thickness less than 50 nm are observed holes in the mask, which lead to retrevo silicon layer under the mask of poly resin. When the thickness of the mask for etching of more than 150 nm cannot be obtained nanowires necessary width (10÷30 nm).

The invention is illustrated in the following description and the accompanying figures.

Figure 1 shows the image of silicon nanowires with ohmic contacts on the dielectric layer on a silicon substrate obtained in an optical microscope, where 1 is a silicon nanowires, 2 - ohmic contacts, 3 - dielectric layer on a silicon substrate.

Figure 2 shows the image of silicon nanowires obtained in the scanning electron microscope, where 4 - slice of silicon nanowires with a width of ~0 nm.

Figure 3 shows the measured effect of the field on the conductivity of silicon nanowires of nanosensor when using the substrate as the lower bolt, which is characterized by high sensitivity of the nanowires to the external electrical influences, with 5 - volt-ampere characteristic (VAC) of silicon nanowires in dependence of the current on the voltage on the ohmic contacts at different voltage on a silicon substrate (20÷50).

For the implementation of the proposed method of manufacturing nanosensor the silicon layer of nanometer thickness is etched in a thread a couple of diferida xenon:

For this pilot was picked up by the etching vapor diferida xenon with the following relevant modes. As the mask for etching was used, the polymer is polymethylmethacrylate.

The thickness of the silicon layer along with the optical density of the silicon control method of ellipsometric measurements. The depth of etching of the silicon controlled using a scanning electron microscope, which allows to obtain an image of the surface produced offered by way of the nanowires and the depth of the gas etching of the silicon layer. In the proposed method, this value was 11÷45 nm.

The duration of the etching gas of silicon nanowires vapor diferida xenon (XeF 2) is determined by the thickness of the base forming a layer of silicon. In the proposed method, this parameter varies from 0.3 min to 1.3 minutes Completeness etching source forming a layer of silicon controlled by electrical measurements of leakage currents between adjacent nanowires.

As examples of implementation of the proposed method cited the following examples.

Example 1

As the substrate using a semiconductor wafer of silicon with a thickness of 350 μm with grown on her thermal oxide of silicon with a thickness of 300 nm. As a semiconductor, which is the source material forming the layer using the silicon caused by the method DELICUT in a layer thickness of 11 nm. For the formation of nanowires with ohmic contacts, the source forming the silicon layer poison vapor diferida xenon with a speed of 36 nm/min at a temperature of 5°C, within 0.3 min through a mask made of poly resin with a thickness of 50 nm.

By nanowires of silicon of a thickness of 11 nm and a width of 30 nm. Created nanowires proposed method have smaller dimensions in comparison with the known technical solutions (see figure 2), the minimum width of the nanowires is ~30 nm.

Example 2

As the substrate using a semiconductor wafer of silicon with a thickness of 350 μm with grown it t is recheckin oxide of silicon with a thickness of 300 nm. As a semiconductor, which is the source material forming the layer using the silicon caused by the method DELICUT in a layer thickness of 25 nm. For the formation of nanowires with ohmic contacts, the source forming the silicon layer poison vapor diferida xenon at a speed of 60 nm/min at the temperature of 15°C for 0.7 min through a mask made of poly resin with a thickness of 100 nm.

By nanowires of silicon of a thickness of 25 nm and a width of 30 nm. Created nanowires proposed method have smaller dimensions in comparison with the known technical solutions (see figure 2), the minimum width of the nanowires is ~30 nm.

Example 3

As the substrate using a semiconductor wafer of silicon with a thickness of 350 μm with grown on her thermal oxide of silicon with a thickness of 300 nm. As a semiconductor, which is the source material forming the layer using the silicon caused by the method DELICUT in a layer thickness of 45 nm. For the formation of nanowires with ohmic contacts, the source forming the silicon layer poison vapor diferida xenon at a rate of 100 nm/min, at a temperature of 20°C, for min 1,3 through the mask of poly resin with a thickness of 150 nm.

By nanowires of silicon of a thickness of 45 nm and a width of 30 nm. Created nanowires pre the proposed method have smaller dimensions in comparison with the known technical solutions (see 2), the minimum width of the nanowires is ~30 nm.

Thus, the proposed method of manufacturing nanosensor allows to reduce the dimensions of the nanowires, as well as to improve electrical properties generated by this method nanowires: to reduce the leakage currents through the lower dielectric layer, to increase the manageability of nanosensor by expanding the range of voltages from the bottom of the shutter and to increase sensitivity nanosensors due to the greater conductivity at a lower concentration of charge carriers.

On the other hand, the positive effect of this invention is to microminiaturization nanosensors on SOI (silicon-on-insulator), which leads to improved reliability, performance, sensitivity, and the degree of integration while reducing their costs and improving environmental performance of the production process, compliance with sanitary and hygiene standards, as well as achieving full compatibility with industrial silicon VLSI technology.

The method of manufacturing nanosensor, namely, that on a silicon substrate to create a dielectric layer on the surface of which is formed a silicon layer, which through a mask by etching to form the nanowires with ohmic contacts, wherein the etching for the formation of nanowires with ohmic the contacts of a given size is carried out in vapor diferida xenon with a speed of 36÷100 nm/min, when the temperature 5÷20°C, within 0.3÷1,3 min, the silicon layer from which the etching form the nanowires with ohmic contacts, create thickness 11÷45 nm, and as a mask for etching using the mask of poly resin thickness of 50÷150 nm.



 

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