CN101549853B - A processing method for constructing nano-protrusion structures on the surface of single crystal silicon based on friction induction - Google Patents

Abstract

A processing method based on friction induction structure monocrystalline silicon nanometer convex structure adopts a diamond needle point with a spherical crown-shaped tip part as a processing tool on a scanning probe microscope to scan the surface of a monocrystalline silicon material; the load applied on the diamond needle point is 0.02-1 times of the critical theoretical load of the surface of the monocrystalline silicon material, and a linear or planar convex structure with other complex shapes can be processed and formed on the surface of the monocrystalline silicon material. The method does not need an external electric field in the implementation process, does not need any chemical treatment on the surface of the material, and has no pollution to the environment; as long as a certain load is applied to the surface of the material through the needle point, a nano-scale convex structure can be processed on the surface; the processing process is simple; the processing repeatability is good; the mechanical stability of the protruding structure is good. The processing uses the needle point with large curvature radius, and the used load is small, and the service life of the needle point is long.

Description

A processing method for constructing nano-protrusion structures on the surface of single crystal silicon based on friction induction

technical field

The invention belongs to the technical field of nanometer processing, and can be used for processing nanoscale convex structures on the surface of materials.

Background technique

Micro-nano processing technology is an important part of modern high-tech industry. The development of micro-nano processing technology has promoted the development of integrated circuits, leading to an increase in the integration level of integrated circuits at a rate of doubling every 18 months. In recent decades, the research of nanoelectronic devices has made rapid progress. However, turning these research results into circuits and devices with computing functions still relies on advanced nanofabrication and fabrication techniques. Since the typical size of nanoelectronic devices is on the nanometer scale, traditional machining techniques such as cutting are no longer suitable for the processing of its components. In addition, with the development of integrated circuits, the manufacture of new circuit chips with extremely fine structures also brings great challenges to traditional nanofabrication techniques. While improving the original processing technology, it is imminent to seek a new generation of nano-processing technology.

Most nanoelectronic devices are composed of various nano-dots, nano-wires and nano-protrusions. Therefore, the key to its fabrication lies in how to realize the controllable processing of these nano-protrusion structures. According to different principles, the current nanofabrication methods mainly include:

Photolithography technology: Using the principle of optical-chemical reaction and chemical and physical etching methods, the circuit pattern is transferred to the single crystal surface or dielectric layer through the template. It is currently the only processing technology used for mass production of micro/nano devices. With the continuous improvement of processing precision, the cost of this method is getting higher and higher, and its technical limitations are further highlighted, such as: it is difficult to eliminate the defects of the mask base plate, and it is difficult to improve the surface flatness of the silicon wafer and the mask plate As well as problems such as the parallelism between the two, the expensive photoresist of the light source, and the easy pollution of the optical system. In short, with the development of nanofabrication technology, photolithography technology has gradually developed to its "application limit".

Single-atom manipulation based on scanning tunneling microscope: A bias voltage is applied between the probe of the scanning tunneling microscope and the surface of the specimen, and the desired nanostructure can be processed by moving and arranging the atoms adsorbed on the surface of the substrate by the needle tip. This method is limited by accuracy and continuity, and the processing efficiency is low, so it is difficult to put it into actual production.

Anodization method based on scanning probe microscope: a processing method to form nano oxide structure through tunnel current action and electrochemical reaction between scanning probe and sample. During processing, the probe is the cathode of the electrochemical reaction, and the sample is the anode, which can oxidize several atomic layers on the surface of the test piece. The processing accuracy of this method is affected by factors such as the sharpness of the probe, the bias voltage between the probe and the specimen, the ambient humidity, and the scanning speed. Since the anodic oxidation method requires the sample to be conductive, it can usually be used to process metal and semiconductor samples, but it cannot do anything about insulating samples such as non-metallic and organic substances.

Scanning probe microscopy can achieve atomic-level processing precision, and methods such as multi-probe parallel processing can effectively improve processing efficiency. Probe technology has broad application prospects in the manufacture of nanoelectronic devices. However, the existing scanning probe microscope nanofabrication methods usually require the application of an electric field, many control conditions, and the operation process is complicated. Therefore, there is an urgent need to study and propose a new method for fabricating nano-protrusion structures with a simple scanning probe.

Contents of the invention

The purpose of the present invention is to provide a method for processing the nano-protrusion structure on the surface of single crystal silicon with simple operation process. The method is simple in operation, high in precision, good in repeatability and high in reliability, and can provide a new way for nanometer processing.

The present invention realizes its purpose of the invention, and the adopted technical scheme is: the diamond probe that tip is spherical crown is installed on the scanning probe microscope, the monocrystalline silicon chip is fixed on the sample stage of scanning probe microscope, starts Scanning probe microscope, apply a set load F to the scanning probe, and make the needle tip mark on the surface of the single crystal silicon wafer along the set track to process the nano-protrusion structure on the surface of the single crystal silicon; wherein , the value of the load F applied to the scanning probe is determined as follows:

(1) by the formula $\frac{1}{\mathrm{E.}}=\frac{1-{\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="H2009100592728E00011.png,H2009100592728E00022.png"\; state="\{\{state\}\}">v</figure-callout>}}_1^2}{{\mathrm{E.}}_1}+\frac{1-{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="H2009100592728E00011.png,H2009100592728E00031.png"\; state="\{\{state\}\}">v</figure-callout>}}_2^2}{{\mathrm{E.}}_2}$ Calculate the equivalent elastic modulus E, where v ₁ and v ₂ are the Poisson's ratios of the needle tip and single crystal silicon respectively, and E ₁ and E ₂ are the elastic moduli of the needle tip and single crystal silicon respectively;

(2) by the formula $f_{}$${}_0=\frac{{{\mathrm{\&sigma;}}_c}^3{\mathrm{\&pi;}}^3{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009100592728E00011.png,H2009100592728E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{6{\mathrm{E.}}^2}$ Calculate the theoretical critical load F ₀ corresponding to the critical stress at which the surface of the single crystal silicon wafer breaks, where σ _c is the hardness of the single crystal silicon, and R is the radius of curvature of the diamond tip.

(3) The load F applied by the scanning probe is 0.02-1 times of the theoretical critical load F ₀ .

Compared with prior art, the beneficial effect of the present invention is:

1. The present invention does not require an external electric field and does not need special chemical treatment on the surface. The specific raised structure required by the nanoelectronic device can be formed directly by mechanical processing. The operation process is simple and the processing efficiency is high.

2. Line-scan (mark) the scanning probe according to the set linear trajectory to obtain a linear nanoscale raised structure; use the scanning probe to perform surface scanning (marking) on the selected area , which can be made into a planar convex structure. The height of the raised structure is determined by the applied load and the number of scratches, and the width is determined by the size of the tip of the probe. It has good processing repeatability and high precision, and can make raised structures with different widths and heights according to actual needs.

3. The protruding structure formed by the method of the present invention is mainly formed by the surface of the single crystal silicon material being subjected to a force less than the critical load of surface failure applied by the probe; it is not formed by the adhesion of foreign substances, and the chemical reaction does not play a leading role. The raised structure is well combined with the substrate and has good mechanical stability.

4. The tip of the diamond needle used for processing is a spherical crown, which has a low wear rate and a long service life.

5. In order to observe or evaluate the processing effect online, in order to achieve high-precision customized processing, it is possible to scan the processing area directly with a probe dedicated to scanning topography without removing the sample after processing the first sample ( The load used in the scanning process is less than 10nN, which is less than 1/1000 of the theoretical critical load F ₀ and will not cause damage or other effects on the surface), and the three-dimensional morphology of the raised structure processed on the sample surface can be observed. If the raised height of the sample is not enough, the diamond probe can be used for the second processing until it is processed into a qualified product. After passing the test of a small number of samples, the processing parameters can be conveniently and accurately set, and high-precision processing can be carried out in large quantities. There is less waste in the process of processing, and the qualified rate is high.

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

FIG. 1 is a linear protrusion structure obtained by processing the surface of a single crystal silicon material by the method of Embodiment 1 of the present invention. The specific parameters of the material processing in the figure are: the crystal plane orientation of the single crystal silicon wafer is (100), the thickness is 0.5mm, the scanning probe microscope (SPM) adopts the SPI3800N type, the scanning probe is a diamond tip, and the elastic coefficient of the cantilever beam is It is 180N/m, and the radius of curvature of the crown tip of the diamond tip ball is about 430nm.

Among them, the processing loads corresponding to sub-graphs a1-a4 are all 135 μN, and the number of scanning cycles is 1 time, 20 times, 100 times, and 500 times respectively;

The number of scanning cycles corresponding to the b1-b4 sub-images is 200 times, and the corresponding processing loads are 45, 55, 85, and 135 μN, respectively.

Figure 2 shows that the convex structure made by the present invention has no change after ultrasonic cleaning in pure water for 20 minutes. (a) and (b) are the morphology before and after cleaning, respectively.

FIG. 3 is a planar protrusion structure processed on the surface of Si(100) according to Embodiment 1 of the present invention. The load used was 85 μN, the number of scans was 11, and the size of the planar protrusions was 5 μm×5 μm.

Fig. 4 is a nano-dot structure processed on the surface of Si (100) according to an embodiment of the present invention. The load used was 10 μN, the scratch length was 20 nm, and the number of scratches was 100 times.

Fig. 5 shows "TRI" written on the surface of Si(100) by the method of Embodiment 1 of the present invention. The load used for writing was 50 μN, and the number of scratching cycles was 50 times.

Figure 6 shows the word "TRI" processed on the surface of single crystal silicon (100) by using a tip with a radius of curvature R of about 100nm: the used load is 150nN, and the number of scoring cycles is 100 times on the surface of single crystal silicon (100) result.

Fig. 7 shows a linear convex structure processed on single crystal silicon (100) by using a needle tip with a radius of curvature R of 5000nm: the load used is 1mN, and the number of scribing is 1 time.

Detailed ways

Example

A specific embodiment of the present invention is: a processing method based on friction induction to construct nano-protrusion structures on the surface of single crystal silicon, and its specific method is:

Install the diamond probe with a spherical crown on the scanning probe microscope, fix the single crystal silicon wafer on the sample stage of the scanning probe microscope, start the scanning probe microscope, and apply the set load to the scanning probe F, and make the needle tip along the set track to carve the surface of the single crystal silicon wafer to process a nano-protrusion structure on the surface of the single crystal silicon; wherein, the value of the load F applied to the scanning probe is as follows Method to determine:

(1) by the formula $\frac{1}{\mathrm{E.}}=\frac{1-{\mathrm{<figure-callout\; id="1"\; label="v"\; filenames="H2009100592728E00011.png,H2009100592728E00022.png"\; state="\{\{state\}\}">v</figure-callout>}}_1^2}{{\mathrm{E.}}_1}+\frac{1-{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="H2009100592728E00011.png,H2009100592728E00031.png"\; state="\{\{state\}\}">v</figure-callout>}}_2^2}{{\mathrm{E.}}_2}$ Calculate the equivalent elastic modulus E, where v ₁ and v ₂ are the Poisson's ratios of the needle tip and the single crystal silicon wafer respectively, and E ₁ and E ₂ are the elastic moduli of the needle tip and the single crystal silicon wafer respectively;

(2) by the formula $f_{}$${}_0=\frac{{{\mathrm{\&sigma;}}_c}^3{\mathrm{\&pi;}}^3{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="H2009100592728E00011.png,H2009100592728E00031.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{6{\mathrm{E.}}^2}$ Calculate the theoretical critical load F ₀ corresponding to the critical stress at which the surface of the single crystal silicon wafer breaks, where σ _c is the hardness of the single crystal silicon, and R is the radius of curvature of the diamond tip.

(3) The load F applied by the scanning probe is 0.02-1 times of the theoretical critical load F ₀ .

The radius of curvature of the spherical crown tip portion of the scanning probe of this example is 100 nm-5 μm (5000 nm).

The monocrystalline silicon wafer in this example can be cleaned before processing, and the specific method of cleaning is to ultrasonically clean in chloroform, acetone, and pure water in sequence. In this way, the adverse effects of pollutants on the surface of the material on the processing process and the formed structure can be avoided.

The following are several specific processing test processes and results using the method of this example:

The radius of curvature of the diamond tip used in tests 1 to 4 is 430nm. Since the hardness of the single crystal silicon wafer is 13GPa, the Poisson’s ratios v ₁ and v ₂ of the diamond and the single crystal silicon wafer are 0.28 and 0.07 respectively. The elastic moduli E ₁ and E ₂ of the silicon wafer are 130 and 1141 GPa, respectively. According to the formulas of (1) and (2), in tests 1-4, the critical load F ₀ applied by the diamond tip should be 135 μN, so the load applied to the diamond tip should not be higher than 135 μN.

1. Processing test of linear protrusions:

The specific conditions and parameters selected during processing: the sample is a single crystal silicon wafer with a thickness of about 0.5 mm, and its crystal plane orientation is (100). The SPI3800N scanning probe microscope is used as the processing equipment, and the scanning probe used is a diamond tip. , the elastic coefficient of the cantilever beam is 180N/m, and the radius of curvature of the tip of the crown of the diamond tip ball is about 430nm. In the test, the loads were selected as 45, 55, 85, and 135 μN, and the number of cycles during marking was selected as 1, 20, 50, 100, 200, and 500 times, and the trajectory set during marking was a straight line.

Using the above parameter conditions, a number of monocrystalline silicon wafers were processed and tested, and the results showed that good convex structures could be formed on the surface of single crystal silicon.

For the above-processed single crystal silicon wafer, the sharp silicon nitride tip with a small radius of curvature (about 30nm) dedicated to scanning topography can be used to scan the processed area in situ under low load (less than 10nN). A processed linear convex structure is obtained. Accompanying drawing 1 has provided the part topography wherein. Among them, the processing load corresponding to a1-a4 is 135 μN, and the number of scanning cycles is 1 time, 20 times, 100 times, and 500 times respectively; They are 45, 55, 85, 135μN respectively. It can be seen from the various topography images that the width of the linear raised structure can be controlled from tens of nanometers to hundreds of nanometers, and the height can reach 10 nm; the width and height of the raised structure are positively correlated with the number of cycles and the applied load.

Figure 2 shows the appearance of the convex structure before and after ultrasonic cleaning in pure water for 20 minutes. Figure 2 shows that the mechanical stability of the convex structure prepared by the present invention is good, and there is no change before and after cleaning. .

2. Processing test of planar protrusions:

The specific parameter load selected during processing is 50μN; the surface scanning method (that is, the trajectories of two adjacent scanning lines are adjacent to each other), the scanning area is 5μm×5μm, and the scanning step size (the distance between two adjacent scanning lines) is 19.5nm , and the scanning frequency is set to 2Hz (that is, two line scans are completed per second). The number of scans is 11, and the rest of the processing conditions and parameters are the same as the processing of the above-mentioned linear protrusions.

The silicon nitride needle tip was used to scan the processed area in situ, and a planar raised structure as shown in Figure 3 was obtained, with a height of 4nm.

The processing test of planar protrusions also shows that with the increase of load and scanning times, the height of planar protrusions will increase accordingly. The minimum area can be controlled in tens of square nanometers.

3. Processing test of nano-bumps:

The specific parameters selected during processing are that the load is 10 μN, the track of the diamond tip is set as a fixed point, the marking (cycle) is 100 times, and the marking length is 20 nm. The rest of the parameters and conditions are exactly the same as the processing of the above-mentioned linear protrusions.

After the scribing is completed, a highly sensitive silicon nitride tip is used to scan in situ to characterize the scribing effect. The results are shown in Figure 4. The height of the nano-dot is about 1.4nm, and the diameter is about 100nm.

4. Machining test of convex structure with complex shape:

The specific parameters selected during processing: the load is 50 μN, the number of cycles is 50, and the scanning frequency is 2 Hz. The rest of the parameters and conditions are exactly the same as the processing of the above-mentioned linear protrusions. The set scanning track is stroke by stroke in the word "TRI". The corresponding angle and length of each stroke are set, such as the horizontal "one" and vertical "丨" of "T" are respectively set to the scanning line trajectory of 0°, 2μm and 90°, 3.5μm; the rest of the processing parameters The conditions are also exactly the same as the processing of the linear protrusion structure.

A silicon nitride needle tip with high scanning sensitivity is selected to scan the writing area, and the writing effect obtained is shown in Figure 5. It can be seen from FIG. 5 that the method of the present invention can be used to write a complex-shaped convex structure with the shape of "TRI" according to the set requirements.

Apparently, the present invention can set different scoring tracks according to needs, and process different convex structures of various complex shapes.

5. Processing test of diamond tip with a radius of curvature of 100nm

The specific parameters selected during processing are: the radius of curvature of the tip of the diamond tip is about 100nm, and the theoretical critical load _F0 of the damage on the surface of the single crystal silicon wafer calculated by formulas (1) and (2) is 7500nN; The load is 150nN (0.02 times the theoretical critical load), and the number of marking cycles is 100. The rest of the processing conditions, parameters and processes are all the same as those of the complex-shaped convex structure in the above test 4. The shape obtained by scanning is The morphology of the “TRI” raised structure is shown in Figure 6.

6. Machining test of a diamond tip with a radius of curvature of 5 μm

The specific parameters selected during processing are: the radius of curvature of the tip of the diamond tip is 5 μm, and the theoretical critical load F ₀ for damage to the surface of the single crystal silicon wafer calculated by formulas (1) and (2) is 18 mN. The load used in this test is 1mN (0.06 times the theoretical critical load), and the scoring cycle is 1 time. The rest of the processing conditions, parameters and processes are all the same as the processing of the linear convex structure in the above test 1. The morphology obtained by scanning is as follows: Figure 7.

Tests have proved that the thickness of the raised structure processed by the present invention is positively correlated with the number of cycles, but as long as the applied load is within the range of 0.02-1 times of the theoretical critical load, the raised structure can be processed on the surface of single crystal silicon. The applied load is 0.02 times of the theoretical critical load, and the cycle is 100 times, or the applied load is 0.2 times of the theoretical critical load, and the cycle is 1 time, and the obvious convex structure can be processed. If a thicker raised structure needs to be machined, this can be achieved by applying a higher load and/or increasing the number of cycles.

Claims (1)

1. A processing method based on friction induction to construct nano-protrusion structures on the surface of single crystal silicon, its specific method is: a diamond probe with a spherical crown at the tip is installed on a scanning probe microscope, and a single crystal silicon wafer is fixed on On the sample stage of the scanning probe microscope, start the scanning probe microscope, apply the set load F to the scanning probe, and make the needle tip scratch the surface of the single crystal silicon along the set track, then the single crystal A nano-protrusion structure is made on the silicon surface; the radius of curvature of the spherical crown tip of the scanning probe is 100nm-5 μm; wherein, the value of the load F applied to the probe is determined as follows: (1) by the formula

Calculate the equivalent elastic modulus E, where v ₁ and v ₂ are the Poisson's ratios of diamond and single crystal silicon respectively, and E ₁ and E ₂ are the elastic moduli of diamond and single crystal silicon respectively; (2) by the formula

Calculate the theoretical critical load F ₀ corresponding to the critical stress at which the surface of the single crystal silicon wafer is damaged, where σ _c is the hardness of the single crystal silicon, and R is the radius of curvature of the diamond tip; (3) The load F applied by the scanning probe is 0.02-1 times of the theoretical critical load F ₀ .

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